Fish

What Causes White Growth on Fish—Cotton Wool Disease

What Causes White Growth on Fish—Cotton Wool Disease

AquariaWise is a participant in the Amazon Associates program and a few other affiliate programs and may earn from qualifying purchases at no extra cost to you. However, we have vetted every program in this guide and believe they are the best for generating affiliate revenue. You can read our full affiliate disclosure in our privacy notice.

Bad health in fish is not uncommon in aquariums, though the foremost cause is puny water condition, which is entirely preventable. The basic rule of thumb is clean water, safe and happy aquatic friends.

Of all the ailments, fungal infections are particularly common and seem to be always lurking in aquariums, probably because fungal spores are present in all tank environments, even with flawless maintenance.

Opportunely, fungal infections are almost always external, thus are easy to identify even for fish keepers without much experience. They bear a characteristic white, fluffy appearance hence commonly called cotton wool disease.

Even so, white growth of the cotton wool disease is sometimes confused with a bacterial infection called cottonmouth (Columnaris), which also affects tropical aquarium fish and manifest in white or greyish white spots.

Another ailment that shows white growth and might be what you are dealing with is the Lymphocystis virus. Small white-pin-prick-like growths appear on a fish’s fins or skins in the early stages and soon clumps together to form cauliflower-like lumps on the coat, mouth, flippers, and occasionally the gills.

Read on for more insight on fish diseases that appear as white growth on fish, including cotton wool disease. We’ll look at how to identify and treat each of the conditions discussed.

That said, please note that the author of this article is not a veterinarian and the points made herein are Aquariwise honest opinion, informed by years of fish keeping and extensive research.

Cotton Wool Disease in Aquarium Fish

Cotton wool disease is a general term used by aquarists to refer to one or more common fungal infections that infect a fish’s skin, fins, or mouth.

The most common fungi types that cause infections on aquarium fish are Saprolegnia and Achlya, though not the only ones. Also, note that there may be more than one species on the site of an infection on a fish’s body.

Usually, the white growth of the fungus often colonize areas where there have been previous infections, parasites, or injuries.

As such, the cotton wool disease is common in tanks with injured fish either from nippings, fin and tail rot, ammonia burns, or wounds unrelated to infections and nippers such as heater burns.

A stressed or diseased fish is also more susceptible to cotton wool diseases (fungal infection), plus poor water quality will exacerbate the ailment even in seemingly healthy fish. (see more).

An infection starts-off as white marks around a fish’s injured area and then spread into a white-fluffy cottonwool-like growth. Depending on the situation, other symptoms may include reddened ulcers on the body and frayed fins.

How Do You Treat Cotton Wool Disease in Fish

Treatment for cotton wool disease in aquarium fishes includes baths using aquarium salt or treating your fish with store-bought antifungal treatment such as Api Fungus Cure.

If you decide to go the salt bath route, it is advisable that your research how well the species of ornamental fish you have handles saline water.

Fishes like mollies, platies, and guppies will withstand elevated salinity and will survive an extended salt bath, but other (most) tropical freshwater species, including goldfish and betta, can only handle a short and mild dip.

Prepare the salt bath for your fish by adding four teaspoons of salt to a clean bucket, then gradually add a gallon of water from your fish tank while swirling the container to dissolve the salt fully.

Once the salt is dissolved completely dissolved, dip your fish in the bucket for between 5 and 30 minutes, making sure you match the duration to the fish your have.

As is expected, guppies, mollies, swordtails, platies, and other hardy fishes should handle better than your goldfishes, bettas, tetras, and cories.

Another remedy that helps when dealing with fungus (cotton wool disease) in fish is doing 30 to 50 percent water change, coupled with regular cleaning of your aquarium.

If only one or a few of your fishes are infected, moving them to a quarantine tank is advisable to ensure the tankmates remain healthy.

You may also want to remedy other issues that yield fungus infections such as an underlying ailment, nippings, and burns. Ensure the ammonia levels in your tank remain at 0ppm, and separate any nippers from other fishes.

Use API Melafix or Furan 2 to heal bacterial infections, repair fins, ulcers, and open wounds to prevent secondary infections including fungus.

Cotton Mouth Disease in Fish

Cottonmouth is a bacterial infection in fish that is often mistaken for a fungus infection because of its white fluffy, mold-like lesions. But unlike fungal forms, Columnaris can be external or internal and is more likely to follow a chronic or acute course.

The ailment is caused by the gram-negative, aerobic, rod-shaped bacteria called Flavobacterium columnare, which enters a fish’s body through the gills, mouth, and small wounds.

As I mentioned, the infection can be both external and internal, but it mostly manifests from the outside, starting first as white to grayish spots on the head, and around fins and gills.

One of the first signs of cottonmouth in fish is a change in the color of the fish’s lips. They mutate from their usual shade to white or grey; white-hair-like sprouts may also emerge.

Patches are usually more apparent on paler fishes or on areas of a fish’s body that lack the natural shimmer as the entire frame.

From white, affected areas regularly turn yellowish or brownish, and the skin around may be tinged red. Lesions in chronic cases progress slowly, taking many days before culminating in a fish’s death.

Other hints that are common with affected fish include white lines around the mouth, clamped fins and lethargy, thickened slime coat, rotting flesh, and eventually untimely death.

Essentially, the Columnaris bacteria are most likely to affect fish that have been stressed by conditions such as poor water quality, inadequate diet, or stress from handling and shipping.

Also note that unlike fungus, cottonmouth disease is highly infectious and may spread through contaminated nets, containers, and even food. As such sterilize such items, and if possible quarantine affected individuals and clean your fish tank.

see more insight: Thespucepets

How Do You Treat a Fish with Cottonmouth

Several remedies work towards dealing with cotton mouth disease in fish. Using salt, including saline baths and adding aquarium salt in your water is quite efficient especially when fighting mild infections.

Adding salt in your aquarium treats all fish in the tank, while saline baths and salt rubs work best on affected individuals.

Use 1 to 4 teaspoons of salt per gallon of water to add to your fish tank or bath your fish for a couple of minutes, but be cautious when treating fragile fishes such as catfish.

Livebearer will enjoy and benefit from the additional salinity in the tank, baths, and rubs.

Infections can also be treated with antibiotics, chemicals in water, or both. Terramycin and Aureomycin are ideal both for baths and when used to treat with food for internal infections.

Copper sulfate, Acriflavine, and Furan work as well, so will a 5 percent Silver Mercury solution applied directly to the diseased areas.

Even so, remember some of these chemicals are harmful to inverts like shrimp and snails, and scaleless fish, so use them sparingly and strictly where need be.

Lymphocystis Virus

Lymphocystis is the last of the three aquarium fish ailments that somewhat manifest in white, cotton wool-like substances on a fish’s body.

However, this is the least common illness of the three covered in this post.

The ailment appears on infected fish as one or more white or beige colored pebbles or wart-like nodules most commonly seen on the fins, skin, or gills, though other tissues may be affected as well.

Quite often, Lymphocystis may also be the cause of pop-eye in fish, which causes the eye to protrude when the virus infects tissues behind the eye.

Overall, the virus hosted in fish causes cells to enlarge many times their usual size, and after about 4 weeks, it may pop and rupture into the water spreading to other fishes in the tank.

Fortunately, dealing with Lymphocystis is much the same as with other contagious diseases in aquariums. With proper precaution, care, and treatment, the affected fish should survive, and other critters in your tank won’t be adversely affected.

That’s all, happy 🦐🐠fish keeping.

Eddie Waithaka

Resident Content Creator and Marketer at AquariaWise who talks about aquariums and fish and aquascapes a lot.

Author image

AquariaWise Newsletter

Get exclusive the tips, that we only share with our subscribers. Enter your email address below.

Your subscription could not be saved. Please try again.
Your subscription has been successful.

This site uses cookies. By continuing to browse the site, you are agreeing to our use of cookies. Okay, thanks