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Performing partial water changes every week or so is an essential part of your aquarium maintenance routine. But even though keeping your aquarium water in good condition and free from toxins is crucial for good fish health, your fishy friends can get pretty stressed out during the process.

This guide explains how you can make those regular water changes much less stressful for your fish. I’ve also included some helpful tips on how to spot the signs of stress in your fish and what you can do to prevent this potentially serious condition from affecting your pets.

Key Takeaways

• Importance of Gentle Water Changes: Weekly water changes are crucial for maintaining a healthy fish tank but can be stressful for fish. It is essential to handle fish carefully with a soft mesh net, avoid major habitat disruptions whenever possible, and ensure gradual changes in water parameters to minimize fish stress.
• Recognizing Fish Stress: Stress in fish can be indicated by behavioral changes such as increased hiding, reduced appetite, rapid breathing, or erratic swimming. Long-term stress can weaken their immune system, making them susceptible to bacterial diseases and parasite attacks.
• Stress-Reducing Techniques: To reduce stress during water changes, it’s recommended to perform smaller, more frequent changes, use a drip system for gradual water introduction, carefully match water temperatures, acclimate fish properly, and use a water dechlorinator and stress coat additives.

Why Do Water Changes Cause Stress?

Although water changes in your fish tank are essential to keep the water clean and safe for your fish, they can cause stress in fish for several reasons:

Handling Stress

If you need to carry out a major water change, such as when taking down your tank for a deep clean or during a house move, you’ll need to move your fish physically.

Handling your fish is extremely stressful for them and should be done as infrequently as possible. Never try to pick up your fish with your bare hands! That’s seriously going to stress them out and could easily end in an accident.

Trying to scoop the fish up in a cup or jug is also likely to cause stress, especially if numerous attempts are needed to catch the fish.

Instead, use a proper fish net with fine, soft mesh to catch and move your fish. Try to avoid chasing the fish around the tank, as that’s sure to stress them. Be patient and allow the fish to settle, carefully nudging them toward a spot in the aquarium where you can get them safely into your net with minimal fuss.

Habitat Disturbance

When carrying out a water change, you generally need to move tank decorations and disturb the substrate with an aquarium vacuum cleaner to remove fish waste and uneaten food. Although necessary to do a thorough job, all that activity can disrupt the fish’s sense of security and territory.

In addition, some hobbyists like to move their tank ornaments around to provide the fish with a change of scenery and give human onlookers a fresh view of the tank. That’s quite a good idea for fish like bettas, who are territorial and intelligent and need plenty of mental stimulation to keep them happy. However, other fish species can become stressed when their environment suddenly changes or feel exposed without their usual hiding spots. You often get the same effect when you add a new decoration or plants to the tank, so allow a few days for the fish to settle down in their new environment.

Changes in Water Parameters

When you replace some of the tank water during a water change, you alter the chemical composition of the water. Even if you’re diligent about matching the temperature and treating the new water with a dechlorinator, subtle differences in pH, hardness, and other parameters can still occur.

Sudden changes in water parameters will stress your fish, as they are highly sensitive to fluctuations in their environment.

Altered Water Flow and Dissolved Oxygen Levels

When you remove water from the tank and then top it up with fresh water, you can change the water’s flow patterns and oxygen levels. Your fish have adapted to specific conditions, and sudden changes in water flow or dissolved oxygenation levels can stress them.

Take care when replacing your filter system that the outflow doesn’t cause a tidal wave where the water was previously calm. That’s sure to upset your fish, especially those that prefer a slow to moderate current.

Introduction of Contaminants

When adding tap water to your aquarium, always use a dechlorinator product to neutralize the chlorine, chloramine, and heavy metals in the water. If you don’t, you risk poisoning your fish, which will definitely stress them.

What Are the Signs of Stress in Aquarium Fish?

The following are all signs of stress in aquarium fish:

• Increased hiding, reduced appetite, excessive aggression, or lethargy can all indicate stress in fish.
• If the fish spend a lot of their time near the water’s surface, gasp for air, and show rapid or labored breathing, that’s a sign of stress, typically related to poor water quality or insufficient oxygen levels.
• Long-term stress can cause fish to lose their color, appearing faded or pale, while some develop blotches or dark patches.
• Stress often causes behavioral changes in fish, like abnormal swimming patterns, darting erratically, swimming upside down, and spinning around.
• If you’ve left the water change for too long, your fish might rub against objects in the aquarium or scratch themselves against surfaces, due to irritation from water quality issues.

Stress is potentially extremely dangerous for fish because it impacts their immune system, leaving the fish weakened and vulnerable to attack by bacteria and parasites.

How To Make Water Changes Less Stressful for Your Fish?

So, how can you make water changes less of an ordeal for your fish and minimize stress?

Take It Slowly

If you forget to carry out a water change one week or simply don’t get around to doing one until a few weeks later, it’s tempting to change half the water in your aquarium or even more.

That’s not great, as the violent changes in water parameters will stress your fish. In addition, beneficial bacteria colonies develop in established aquariums to help break down fish waste and other organic matter. Large water changes can disrupt these colonies, leading to spikes in harmful substances like ammonia and nitrites until the bacteria can re-establish themselves.

Instead of performing a large water change all at once, I recommend breaking it down into smaller, more frequent ones. This helps keep the water parameters stable, reducing the shock and stress to the fish.

Use Drip Systems

The use of a drip system allows for the very gradual introduction of fresh water into an aquarium, replicating the natural flow of water in streams and rivers. That gradual change avoids rapid fluctuations of water parameters and allows the fish to acclimate more easily to the new water conditions.

Avoid Temperature Shock

Temperature shock in aquarium fish happens when the water temperature in their aquarium fluctuates suddenly and significantly.

All fish species, from humble goldfish to glamorous discus, thrive in specific temperature ranges. When the water temperature deviates from this range, it can cause huge amounts of stress and potentially harm or even kill the fish.

So, how can temperature shock affect your fish?

• Sudden changes in temperature stress fish, weakening their immune systems, leaving them more susceptible to diseases, and causing a general failure to thrive.
• Temperature influences the fish’s metabolic rate. Rapid temperature changes can disrupt their metabolic processes, affecting digestion, respiration, and overall physiological functions.
• The water temperature affects the amount of dissolved oxygen the water contains. Warm water holds less oxygen than cool water, so a sudden temperature increase can reduce oxygen levels, leading to oxygen deprivation in fish, which can be fatal.
• Fish suffering from temperature shock can become lethargic, lose their appetite, or even become agitated or erratic in their behavior.

When carrying out water changes, ensure the temperature of the new water matches the tank temperature. To do that, pre-mix the replacement water and wait until it reaches the same temperature as the aquarium.

Use an accurate aquarium thermometer to double-check the water temperature in the tank before adding it to your tank.

Use Proper Acclimation Practices

If you had to take your fish out of the tank during cleaning and changing some water, don’t simply tip them back into the aquarium! That’s sure to stress your pets. The same applies when adding new fish to your tank.

Float the bag with the fish in the tank for around 20 minutes so that the temperatures have a chance to equalize. Then, gradually add a little bit of aquarium water to the bag over a period of time before releasing the fish into the tank.

Sudden bright lights can stress your fish, so it’s also a good idea to leave the tank lights switched off during acclimation to help reduce stress on the fish.

Watch Out for Signs of Stress!

Throughout the acclimation process, watch your fish closely for changes in behavior that could indicate stress. Signs of stress include rapid breathing, erratic swimming, or loss of coloration. If any signs are observed, slow down the acclimation process.

Dechlorinate Tap Water

Tap water contains chlorine or chloramine, chemicals that are extremely dangerous to fish and other livestock. Exposing your pets to untreated tap water could kill them. Sometimes, tap water also includes heavy metals, which are also dangerous to fish.

So, always use a good-quality water dechlorinator to neutralize these chemicals before adding tap water to your aquarium.

Buffer pH

If your tap water has a significantly different pH to that of your aquarium, you might want to consider using a pH buffer to gradually adjust the pH of the replacement water to match that of the tank.

Stress Coat Additives

Many water conditioners include stress-reducing ingredients like aloe vera or vitamin E, which can also promote the healing of damaged tissue. If you’re concerned that your fish get stressed during water changes, adding one of these conditioners can help.

Final Thoughts

Although water changes are essential to maintain a healthy, safe aquarium environment for your fish and other aquatic pets, the disturbance to the habit during vacuuming can be stressful for them. In addition, water parameters can change, and temperature fluctuations can sometimes occur, both of which will stress your fish.

You can prevent fish stress by using gradual acclimation techniques, always dechlorinating tap water before adding it to the aquarium and adding a water conditioner with a stress coat.

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As an experienced fishkeeper, I can tell you that one of the most exciting things you can do is breed successfully from your fish. But where do you start? There’s so much misinformation out there online that it can be a minefield for newbies to fish breeding.

Experts hope to steer the aquarium fish trade away from taking specimens from the wild environment. Wild fish are often caught with poisons that can damage coral ecosystems and in some cases, numbers are becoming seriously depleted. So, the more successful commercial and home breeding operations are, the better it is for our wild fish.

This article discusses the tenworst breeding tips that seasoned aquarium fish breeders have ever heard. We also explain how to go about breeding aquarium fish the right way!

Key Takeaways

• Sustainable fishkeeping is promoted by successful home breeding, which lessens the reliance on wild-caught fish, helping to protect natural habitats and fish stocks.
• Many popular but misguided breeding tips can lead to negative results, such as poor fry survival rates and unhealthy breeding conditions.
• Expert breeding advice emphasizes the importance of controlled environmental conditions, correct feeding strategies, and avoidance of stress-inducing practices for successful reproduction and fry rearing.

Just Let Them Do Their Thing!

Unfortunately, many amateur breeders recommend allowing nature to take its course and letting the fish do their thing without human help. That rather laissez-faire attitude towards breeding can lead to overcrowding, inbreeding, and neglect of proper care for the fry.

Add More Fish for Better Chances

When setting up a spawning tank, you should include breeding pairs of male and female fish that are in excellent health and spawning condition.

Some people recommend adding a few more fish to your breeding tank, mistakenly thinking that will increase the chance of the fish breeding. However, that approach is counterproductive, as introducing more fish into an established breeding tank can stress the breeding pair and disrupt their breeding behaviors.

Skip Water Changes During Spawning

This terrible tip goes hand-in-hand with the recommendation to allow nature to take its course.

Poor water quality will result if you don’t carry out water changes in your spawning tank. When that happens, the fish might not breed at all, and if they do, their fry won’t be healthy and will likely die pretty quickly.

Ideally, you should change around 20% of the breeding tank water daily, vacuuming away any waste during the process. That prevents fish waste and uneaten food from accumulating in the tank, producing ammonia as it decomposes, potentially poisoning your fish.

Feed Only Live Foods

Most fish living in the wild environment eat a varied diet that includes a small amount of algae and plant material. Although feeding your fish live food is undoubtedly good for them, relying solely on those foods can lead to nutritional deficiencies.

Throughout the breeding process and in the build-up to it, feeding your fish a balanced diet of live, frozen, and high-quality dry foods is essential.

Handle the Eggs and Fry Frequently

Some misguided breeders suggest handling the eggs and fry as often as possible. However, excessive handling of eggs or fry causes stress and increases the risk of disease transmission.

Fit a piece of very fine mesh across the tank bottom to prevent the parent fish from eating their eggs. When the eggs are laid, they drop through the mesh and out of the parents’ reach.

However, that approach only works with egg-scattering fish species. If the eggs are deposited on plant leaves or spawning mops, the best thing to do is remove the parent fish so the eggs can develop and hatch safely. In fact, in most cases, it’s best to return the parents to your main tank, leaving the fry to develop and grow in peace.

Of course, there are exceptions, and some fish, such as Kribensis, make very good parents, guarding their young until they can fend for themselves. In that case, you should leave the parents in the spawning tank with their babies.

Keep the Breeding Tank in Total Darkness

Some hobbyists recommend keeping the breeding tank in total darkness to encourage spawning. However, fish need a clear day-night cycle for natural behavior, including breeding.

In the wild, lengthening days and increasing water temperatures tell fish that it’s time to spawn. If you deprive them of light for long periods, the fish won’t breed and could even die.

Use Preventative Medication

Some breeders like to use medications prophylactically to prevent diseases from affecting their fish. However, administering medications without a clear indication can disrupt the delicate balance of the aquarium ecosystem and harm both the breeding pair and their offspring.

Ideally, your fish will be in prime condition before you attempt to breed from them. Provided your spawning tank is clean and correctly set up, you should have no issues with diseases, so preventative medication is not necessary.

Ignore Tank Size Requirements

You’ll read many online articles that recommend using a small tank for breeding purposes.

However, breeding pairs need plenty of space not only for spawning but also to accommodate territorial behaviors and allow proper care of the offspring. If the tank is too small, the fish could become stressed, which could lead to aggression and possible injuries. Also, in some cases, a stressed-out parent will eat its eggs and fry; always provide your fish with a large breeding tank.

Mix Different Species for Hybrid Vigor

Hybrid vigor, also known as heterosis, refers to the phenomenon where the offspring of genetically diverse parents show improved growth, health, a longer lifespan, or other desirable characteristics.

Hybrid vigor arises due to the combination of favorable alleles from each parent, leading to increased genetic diversity and overall fitness in the offspring. That’s why crossbreed dogs are currently so popular. Agricultural breeding programs also use hybrid vigor, crossing different strains of wheat, barley, and the like.

However, when it comes to fish breeding, hybridization often leads to unpredictable results and can produce genetically weak offspring prone to health issues. For that reason, breeding should be done within the same fish species whenever possible.

Don’t Worry About Water Parameters

Ignoring water parameters such as pH, temperature, and hardness can lead to unsuccessful breeding attempts or health issues in the offspring and parents.

For that reason, it’s crucial to maintain stable and appropriate water conditions. Ideally, the water parameters should match those in the main display tank, although the water temperature can be a few degrees warmer, as that often triggers spawning.

For example, Indonesian ornamental fish breeder Tom Bowling tried to breed Blotched Anthias for eight months and failed dismally.

Thinking he was doing the right thing, Bowling kept the fish in cool water, attempting to replicate the temperatures these deep-water fish are typically in in their natural habitat. It was only when his air conditioning unit broke, and the water temperature increased overnight by a few degrees, that he realized his mistake. In the warmer water, the fish immediately began spawning!

Top Fish Breeding Tips!

Now you know how not to do it, here are some top breeders’ tips for successful fish breeding.

When’s the Best Time to Breed Fish?

As we mentioned earlier, most fish species breed in the spring, when the daylight lengthens and the water gets warmer.

You can mimic this in your home fish tank at any time by increasing the water temperature slightly, leaving the lights on for a little longer each day, and performing more frequent water changes.

Provide both male and female fish with high-protein food and create an environment as close to their natural one as possible, and you will condition the fish to spawn. Different fish species have different egg-laying manners, so you must research the species carefully and provide them with suitable breeding surfaces, plant types, and aquarium setups.

How To Choose a Breeding Pair of Fish?

On tropical fish farms in Asia and Florida, fish are encouraged to spawn in spring, usually indoors. The fry is transferred to outdoor ponds to grow before being shipped to aquarium stores. There’s plenty of live food in the ponds for the youngsters to eat from the start, and they are then offered pellets to promote further healthy growth. The young fish will be well-developed and mature enough to breed by the fall.

Start by choosing fish with no obvious physical deformities, of a good size, and with the best colors.

How to Condition Your Fish for Breeding?

Before you can attempt to breed from your fish, you need to bring them into spawning condition.

• Give the fish plenty of high-protein food, feeding them more often than you would usually feed your community aquarium fish, ideally several times every day. Live brine shrimp or frozen meaty foods are ideal for this.
• Provide the breeding pair with their own dedicated spawning tank, set up with the appropriate substrate or decor, depending on the species’ method of egg-laying or livebearing.
• Most breeders recommend keeping male and female fish separate for a few weeks to increase their likelihood of spawning once they get together. To do that, you can use a glass partition in the tank so that the fish can fully view each other.
• Increase the water temperature in the breeding tank by a few degrees to around 78o to 82o degrees F, depending on the species. The idea is to have the temperature slightly warmer than it is in your community tank.

Once you’ve done all those things, the female fish will become loaded with eggs or roe. Throughout the conditioning period, you must also keep the pH, water hardness, and alkalinity in line with what’s required by the species for spawning.

How To Produce Infusoria?

One of the biggest challenges facing novice fish breeders is how to feed the fry. You need a food source small enough for the babies to eat, and most aquarists and fish breeders use infusoria as their fry’s first food.

Infusoria are tiny organisms, including bacteria, algae, crustaceans, and protozoa in the water that the little fry can eat.

Growing infusoria is remarkably simple. Just place a lettuce leaf in your breeding tank as soon as spawning is complete. As the leaf gradually decomposes, enough infusoria are created to provide the fry with food for at least their first week. You can then remove the old leaf and replace it with a new one.

Once the young fish have grown enough, you can feed them finely powdered commercially prepared fry food or paste preparations, like Liquifry. After another couple of weeks, you can offer your fish frozen or live foods, such as bloodworms, daphnia, and brine shrimp.

What Size Spawning Tank Do You Need?

Remember, it’s not good practice to keep your breeding fish in a very small tank, as stress can disrupt the spawning process and stress your fish.

Most beginner fish species will do fine in a 10-gallon breeding tank, although larger species will need more spacious accommodation. Equip your spawning tank with a heater, an air pump, and a sponge filter that won’t trap the tiny fry.

Final Thoughts

There are plenty of terrible fish breeding tips out there on the net that you should ignore. In fact, rather than helping the novice breeder to succeed, much of that advice will guarantee that your fish won’t spawn at all!

For breeding success, condition your breeding pairs before adding them to your spawning tank by feeding them a high-quality diet for a few weeks beforehand. Keep your fish in a spacious breeding tank, carry out daily water changes to keep the environment clean and hygienic, and elevate temperature by a few degrees to trigger spawning.

Most fish species will eat their eggs and fry, so remember to remove the parents once the eggs have been laid.

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If you’re new to the aquarium hobby, you might think that keeping fish is a tad – dare we say it – boring! After all, your pets spend their days swimming around the tank, eating and nibbling on algae, and not really doing much else, right?

However, that’s not the case with every fish species. So read this guide to discover ten fish species known for their playful behavior and interaction, adding a lively dynamic to the aquarium.

Key Takeaways

• Explore the unexpected playful side of pet fish, from Bettas performing tricks to Goldfish interacting with their owners.
• Aquarists can find joy in the unique behaviors and interactive qualities of various fish, including the ornate swimming of Neon Tetras and the symbiotic relationship between Clownfish and their anemones.
• Success in keeping these engaging creatures comes from attention to each species’ environment and nutritional needs, underscoring the rewarding nature of the fishkeeping hobby.

Summary Table

Here’s a handy table summarizing the key facts you’ll need to know if you want to take home any of our featured fish and add them to your aquarium!

Summary Table of Playful Fish Species

Betta Fish (Betta splendens)

Betta fish, also known as Siamese Fighting Fish, are popular freshwater aquarium fish best known for their vibrant colors and fancy, flowing finnage.

Bettas come from Asia, especially Thailand, Cambodia, Laos, and Vietnam, where they inhabit shallow, slow-moving waters like rice paddies, ponds, and marshes. These labyrinth fish are relatively hardy and adaptable, preferring a mainly carnivorous diet of insect larvae, insects, and small crustaceans. That said, they do enjoy nibbling on algae and small amounts of plant matter to supplement their diet.

Betta fish are not only beautiful but also have great personalities! They usually learn to recognize their owners and can be trained to do tricks like swimming through hoops and jumping out of the water to grab a morsel of food from your fingers.

If you’re planning on getting a betta fish for a pet, bear in mind these fish can be pretty aggressive, and you can never keep two males together in the same tank.

Dwarf Gourami (Trichogaster lalius)

The beautiful Dwarf gourami is known for its curious behavior and interactive nature. The species’ vibrant colors and unique patterns make it a firm favorite with aquarists. These fish come in a range of colors, including red, blue, and green, and have a distinctive iridescent, metallic sheen that makes them stand out in any setup.

Dwarf gouramis are quite small, reaching only around 3 inches long at maturity, and are native to the slow-moving waters of South and Southeast Asia.

I love keeping Dwarf Gouramis as pets for their curious nature and interactive behavior. My gouramis seem to enjoy following me when I walk past their tank and dart to the water’s surface to grab a mouthful of air. These curious fish spend much of their day exploring their environment, playing with tank decorations and toys, such as a ping pong ball floating on the surface.

Jack Dempsey Cichlid (Rocio octofasciata)

Jack Dempsey cichlids are popular freshwater aquarium fish known for their playful behavior and unique appearance.

These South American natives are named after the famous boxer due to their aggressive and feisty nature. They can reach 10 inches long when fully grown, so large fish tanks are required to accommodate one of these guys.

Although not renowned for their ability to perform tricks, Jack Dempsey cichlids are still pretty interactive, curious, and playful. These fish have a love of rearranging the hardscape you worked hard to set up, moving rocks and decorations around to their liking. On the downside, Jack Dempseys can be aggressive towards other fish, although they can live with other larger, similarly belligerent species in a large enough tank.

Goldfish (Carassius auratus)

Goldfish are my favorite freshwater fish and have been for over 40 years!

They come in many different varieties, ranging in size from 6 to 8-inch fancy types to 12-inch long pond fish. You can keep most types of goldfish in a large tank, although most are happier living in a spacious garden pond with plenty of swimming space.

In addition to their amazing variety of colors, goldfish can be quite interactive. For example, my goldfish would beg for food whenever I passed their aquarium and would investigate my fingers when I was carrying out water changes and vacuuming the substrate. I even trained my Orandas to take food morsels from my fingers!

Neon Tetras (Paracheirodon innesi)

Fish like Neon Tetras are known for their schooling behavior, which can be fascinating to watch as they dart around the tank and interact with each other.

These brightly colored little fish can be quite skittish, and it’s entertaining to watch them flitting through clumps of dense plants and exploring their tank decorations. Neons are somewhat easier to care for than their slightly larger cousins, Cardinal tetras, and make just as impressive a display when kept in large groups of ten or more.

That said, these swimming gems need a well-maintained tank, stable water parameters, and a high-quality diet to thrive.

Clownfish

The movie Finding Nemo made Clownfish famous, although they were already an extremely popular go-to marine fish that graced many beginner’s saltwater tanks.

These beauties are well-known for their playful antics and interaction with their owners. They beg for food and come up to the viewing panes to see what you’re up to when you pass their aquarium.

Although Clownfish won’t talk to you like the piscine movie star, they will enjoy a symbiotic relationship with their anemone if you provide one. The interactive relationship between the Clownfish and the anemone is a fascinating one. The Clownfish is immune to the anemone’s stinging tentacles, using them as protection from would-be predators. The anemone enjoys devouring the Clownfish’s leftovers and also receives its protection from predators.

Guppies (Poecilia reticulata)

Guppies are lively and colorful fish who enjoy swimming around the tank and interacting with their tank mates. They also breed constantly, so you’ll never be short of replacements for any casualties if you keep this species!

I remember keeping a whole bunch of guppies in a large community tank one time. Those beautiful little fish kept me entertained for hours, their bright colors flashing through the lush plants in the aquarium was quite a site, as they chased each other, and looked for food scraps at feeding time.

Another highly entertaining habit my guppies had was hanging around in the filter outflow, using the current to carry them up to the water’s surface, and diving back down to start the ride over, time and again!

Kuhli Loaches (Pangio kuhlii)

Kuhli Loaches are slender, eel-like fish that are known for their playful behavior, often darting in and out of hiding spots in the aquarium at lightning speed.

These rather cool, oddball fish are fascinating or freaky, depending on how you look at it! Although they don’t eat algae, these weird fish can still make excellent clean-up crew members, scavenging scraps of leftover food. That said, you need to feed them to prevent them from going hungry. The loaches enjoy sinking pellets, frozen bloodworms, and live blackworms.

If you have a moonlight setting on your aquarium lighting unit, try watching the Khuli loaches at night since they tend to be most active and less shy once the sun goes down. You can keep these fish in a planted tank, and they do well in a community tank with snails, shrimp, and other peaceful fish species.

Plecos (Hypostomus plecostomus)

Plecos, also known as plecostomus or sucker-mouth catfish, are a diverse group of freshwater fish belonging to the family Loricariidae. They are popular among aquarium enthusiasts for their distinctive appearance and algae-eating habits.

Several popular species are available, including the bizarre-looking Bristlenose pleco with its bristly snout, the Rubber Lip pleco, and the beautifully colored Gold Nugget pleco. Don’t make the mistake of taking home a juvenile Common pleco unless you have a very large tank since these fish can reach over a foot in length!

Plecos are known for their algae-eating behavior, which helps to keep aquariums clean. These fish are typically nocturnal, spending much of their day resting on surfaces or hiding in caves or crevices. So, if you want to watch them play and interact with their environment, you must be a night owl with a moonlight setting on your tank lighting system!

Corydoras Catfish (Corydoras paleatus)

Corydoras catfish are another of my favorite aquarium fish species and have featured in all my tanks.

These cute little fish only grow to a couple of inches long and come in many different varieties, all of which are peaceful and work well in a community aquarium. Corys come from the coastal rivers in Brazil and Uraguay, especially the lower Paraná River basin, and have been favorites with hobbyists for many decades.

Corys do best when kept in small groups of at least five individuals, sitting on the substrate and resting for much of the day. Then, just when you were watching your other fish cruising gracefully around the tank, a cory flies abruptly up to the surface to snatch a gulp of air before plunging back to the substrate again.

As a bonus, these highly entertaining little fish are incredibly hardy and will provide you with up to seven years of fun.

Final Thoughts

If you thought keeping fish was a boring hobby, I hope this article has made you think again!

As you’ve learned, you can keep many highly entertaining, playful, interactive fish in a basic freshwater aquarium setup. Provided you give your chosen fish species a well-maintained environment and a high-quality diet, your aquatic pets should provide you with years of fascinating viewing.

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If you’ve been in the aquarium hobby for a while, you’ll probably have heard of UV sterilizers. By passing water through UV light, the sterilizer reduces the number of algae and bacteria suspended in the water column.

But while many people claim that UV sterilizers are useful for clearing up cloudy or green water, there are other ways to do that, too. So do you really need this optional aquarium accessory? Here, you’ll find out.

What Is a UV Sterilizer?

A UV sterilizer is an optional piece of aquarium equipment used to reduce the presence of algae, bacteria, and other pathogens within the water column.

The unit works by running the tank’s water past a germicidal fluorescent UV lamp that damages the DNA of the microorganisms within the water column, thereby preventing them from reproducing and reducing their numbers within days.

UV sterilizers are usually either standalone units that use a motor to pump water through a sealed chamber or are passive units without a motor that rely on a canister filter to pump water through them.

Very occasionally, canister filters and hang-on-back filters come with UV sterilizers already installed.

When Are UV Sterilizers Used?

Most aquarium owners don’t use UV sterilizers as they are strictly an optional accessory. Those who do choose to keep one typically only turn it on for short periods to treat green or cloudy water, and to help contain bacterial or even parasitic and fungal infections.

For Treating Green or Cloudy Water

UV sterilizers are especially useful in clearing water of algal blooms that turn the water green, or bacteria blooms that make the water cloudy. When effective, UV treatment may even clear the water within a few days.

For Treating Infectious Diseases

Some aquarists also believe that, when used at the right time, UV sterilizers can help to contain outbreaks of parasitic infections like ich and help to reduce the chances of bacterial infections on vulnerable specimens.

While a UV bulb won’t cure fish infections without additional treatments such as medication, it may help to reduce the pathogens from reproducing, as well as reduce the risks of further outbreaks.

Because of this, some aquarists choose to turn their UV units on when their fish are particularly stressed or injured and therefore more susceptible to infection.

When UV Sterilizers Won’t Help

It must be understood that UV sterilizers can only treat microbes that are already suspended within the water column. Organisms that already are floating on the surface or adhered to rocks, glass, plants, gravel, or your aquatic pets won’t run through the unit and are therefore left untreated.

So, while UV can be very effective for treating algae and cyanobacteria suspended in the water, it won’t be much help for treating algae outbreaks on your substrate, glass, and aquarium décor. Similarly, it will only treat parasites in the phase where their offspring are suspended in the water.

Additionally, UV sterilizers are unlikely to help if your water has been stained yellow or brown. Such coloration is usually caused by tannins that are released by materials such as driftwood, peat, or dead leaves.

In some cases, tannins are beneficial, but they can also be removed with a carbon filter if you prefer to get rid of them.

When UV Sterilizes Should Never Be Used: Cycling a New Aquarium

The one instance where UV sterilizers could prove truly detrimental is when a new aquarium is being cycled.

During cycling, beneficial nitrifying bacteria are busy reproducing and spreading themselves around the aquarium. Not only do they take up residency in your filter, but they also proliferate in the tank’s gravel, and even among rocks and plants.

Since the UV light will sterilize any nitrifying bacteria that are suspended in the water and passing through it, it should always be switched off until the bacterial colonies are firmly established and the tank is fully cycled.

The Pros of Using UV Sterilizers

• Clears green water by combating algae and cyanobacteria in the water column
• Clears cloudy water by reducing bacterial blooms in the water column
• Reduces the number of active pathogens such as bacteria, parasites, fungi, and viruses that are suspended in the water
• Motorized models increase water circulation and potentially aeration, too
• Usually quiet and discreet

The Cons of UV Treatment in Fish Tanks

• Extra investment and increased electricity costs
• Bulbs need replacing every 6-24 months (typically around 9 months) if the unit is left on and some models don’t feature replaceable bulbs
• Doesn’t treat algae and pathogens that are adhered to the rocks, plants, glass, or gravel
• May prove ineffective if bulbs are not strong enough or water passes through the unit too quickly

Featured Products

As we’ve already discussed, UV sterilizers either come as stand-alone units or are attached to an existing canister filter. Here we take a closer look at popular models of each kind that have been receiving the most positive reviews from customers.

COODIA Internal Green Water Killer Aquarium Filter Tank U-V Pump

If you want to try a UV sterilizer without breaking the bank, this handy little standalone unit offers a great solution. While much cheaper than models from big brands, customers of the COODIA ‘Green Water Killer’ report equally high satisfaction rates.

The unit runs on just 5 watts of electricity, meaning it’ll add very little to your electricity bill. Handy features like an optional air intake/bubbler and LED light to indicate when the UV bulb needs replacing shows thoughtful design, too.

Suitable for saltwater and freshwater tanks, many customers confirm that it can clear up green water in 3-7 days. While the manufacturers claim it can handle tanks of up to 75 gallons (more than many of its competitors), some users with larger tanks have reported it less effective.

What we like:

• Very inexpensive
• Mostly upbeat reviews suggest the unit is effective in most situations
• Very low 5-watt energy consumption
• Optional air intake allows for increased aeration
• Indicator light signals time for bulb replacement

What we don’t like:

• Equipment from lesser-known brands is sometimes less reliable
• Some customers have reported faulty parts
• Customers with tanks over 50-gallons sometimes report ineffective performance

Fluval In-Line UV-C Clarifier

An efficient passive UV sterilizer from a trusted brand, the Fluval In-Line Clarifier has been designed to attach to canister filters with 5/8” (16 mm) hosing.

As you’d expect from Fluval, the model features innovative technology such as CCFL (Cold Cathode Fluorescent Light) technology that runs cooler than traditional UVC bulbs and lasts up to 30,000 hours (3X longer).

Most customers report high levels of satisfaction with performance and the 2-year warranty offers reassurance that the unit has been made to last.

Important: Please check your canister filter’s hosing diameter is compatible before purchasing, as some models such as the Fluval FX series feature incompatible hosing!

What we like:

• Fluval is a veteran brand renowned for solid workmanship and products you can trust
• Good reviews suggest this sterilizer is effective for a wide variety of applications
• Compact design means the unit is discreet and takes up little tank space
• A 2-year warranty for defective parts and workmanship gives extra confidence in product quality

What we don’t like:

• While the UV bulb is long-lasting, it can’t be replaced
• Not compatible with all sizes of canister filter hosing

Alternatives to UV Treatment

The most common reason for people installing a UV filter is to clear up green or cloudy water, but for that job, other alternatives can be equally effective and sometimes even longer lasting.

Better Tank Maintenance

Green or cloudy water in aquaria usually indicates poor water quality that has become too high in nutrients.

When uneaten fish food, dead leaves, algae, and fish waste break down, nitrates and phosphates are released into the water which causes algae and bacteria to bloom. While UV sterilization might help to reduce the symptoms, it’s much better to tackle the root cause of the problem.

Here’s our quick list of tank maintenance basics for keeping water quality and water clarity consistently high:

Reduce Feeding

Because uneaten fish food and excessive fish waste are such major causes of poor-quality water that becomes cloudy, it’s imperative to avoid overfeeding. Indeed, overfeeding is one of the leading causes of poor water quality and fish health issues, especially for beginners.

To overcome this unnecessary issue, never feed more than your fish can eat within 2 minutes. Clean up any leftover food before it begins to break down and foul your water.

Carbon Filtration

You may have noticed that many aquarium filters on the market feature carbon filtration, but not all aquarists are well-versed in what that means.

Typically, carbon filtration refers to a filter compartment that houses small pieces of activated carbon, also known as activated charcoal. As water passes through the carbon, its sponge-like structure effectively draws out very small impurities that other types of filter media miss.

By reducing small particles, tannins, and certain dissolved nutrients in the water such as phosphates, carbon filters remove the food that problematic algae and bacteria thrive on, effectively reducing their numbers within days.

While results may not be as fast or dramatic as UV sterilization, when combined with good tank maintenance, carbon filters will usually help your water to remain crystal clear in the long run.

The Downsides of Carbon Filtration

If you do decide to install a carbon filter, just be warned that some of the nutrients it filters out are also necessary for plant growth. Phosphates, in particular, are very important for healthy plant growth, meaning that some planted aquarium enthusiasts avoid carbon filtration altogether.

Additionally, carbon will also filter out many types of fish medication as well as tannins from the water. So, if you are attempting to medicate your fish or aiming to create amber-colored, tannin-filled water, carbon filtration isn’t an option.

Conclusion – Do You Need a UV Sterilizer?

After weighing up the pros and cons of UV sterilizers, what’s the verdict? We conclude that most aquarium owners don’t need a UV sterilizer, but some might find one useful.

With proper tank maintenance and the option of carbon filtration, most aquariums should retain clear water, free from excessive algal or bacterial blooms – which renders UV sterilization unnecessary.

On the other hand, if you’ve tried everything else and are still having difficulties in achieving clear water, you could give one a try. UV treatment may be especially appropriate for those who want crystal-clear water without having to use a carbon filter.

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