Fin Rot 

Fin Rot is one of the most common, and preventable, diseases striking bettas. Many new bettas are brought home with the disease, because of poor care and housing at the pet store. Many betta owners face this disease because of misconceptions about betta care. Luckily, it is easy to cure.

* Symptoms
* Causes
* Treatment
* Prevention

red veiltail Symptoms blue veiltail

Fin rot is characterized by damage to any of the fins. This may include small holes (pinholes), ragged or frayed edges, transparent or thin sections of fin, fins falling apart in chunks, edges turning white, black or red, slimey looking areas, or inflamation of the fins or fin base. In crowntails, rays may thin or break off. If left untreated, the fins will become shorter and shorter over time, and fin rot may progress into the body. In advanced cases, the fish may have bloody patches.

Secondary infections such as columnaris (also known as saddleback disease, cotton wool, or fungus) and true fungus may set in.

There are other causes of fin damage, such as rough objects in the tank, "blowing" a fin by flaring too aggressively, or tail-biting. Fin rot can be differentiated by its progression and often has slimey, thin, red or black edges. Fin damage may lead to fin rot, so it is important to keep all bettas with damaged fins especially clean, and use a preventative dose of aquarium salt until the damage has healed.

There are other diseases which may appear to be advanced fin rot. Water mold is characterized by fins with bloody edges which are rapidly eaten away (as in overnight), leaving jagged, bloody sores with fin bones exposed, and reddish or white meaty lesions which can resemble cracks on the fish's body. It can be differentiated from fin rot by the rapid progression, pale patches and lesions, and bloody, boney fin deterioration.

red veiltail Causes blue veiltail

Fin rot is caused by poor water conditions. Essentially, bettas develop fin rot when kept in dirty water. Fin rot is a sign that their tank is not being cleaned often enough.

In these conditions, ammonia (a toxin) builds up and burns the betta's fins, also causing the fish systemic distress and lowering the betta's immune system. Opportunistic gram-negative bacteria (Aeromonas, Psuedomonas, or Vibrio) thrive in the dirty water, and infect the weakened betta.

To prevent fin rot, do adequate water changes on your tank. In an unfiltered tank, you must also rinse the tank and all decor, gravel and equipment in hot water with each 100% change.

red veiltail Treatment blue veiltail

Treatment for fin rot is simple if you catch it soon enough. If you spend time every day observing your bettas, you will be able to identify fin rot in its earliest stages. The earlier fin rot is caught, the easier it will be to treat.

Treatment is pristine, warm water and aquarium salt.

Advanced cases of fin rot can be harder to treat. Fin rot can advance so that the fish has no fin to speak of, and even begin eating away at the fish's body. You may find advanced cases of fin rot in rescued fish from WalMart or chain pet stores (they just don't clean those cups often enough, and do not properly treat sick fish). Monitor your own fish daily so that fin rot never has a chance to progress this far!

In cases of advanced fin rot, frequent water changes and aquarium salt are necessary. The fish should also be treated with an antibiotic that targets gram-negative bacteria, such as minocycline or kanamycin.

When treating a fish with medication, it is important to offer supplemental oxygen. Many medications leech oxygen from the water, and sick fish may have trouble breathing.

An air pump, aquarium hosing and an airstone can be set up to create a bubbler for your tank. Because bettas are still water fish, a high current may be stressful for them, so it is important to put the bubbler on low. Some air pumps are adjustable. Alternately, you can clip the hose with multiple binder clips, or purchase a gang valve to control the output.

red veiltail Preventing Fin Rot blue veiltail

Prevention for fin rot is extremely simple. Almost every case can be prevented with adequate water changes.

In an uncycled tank, 100% of the water should be changed with each cleaning, and the tank and all decor washed with hot water. Waste can be sucked off the bottom of the tank daily (turkey basters are great for this in small betta tanks) to help keep the tank extra clean between water changes.

A one gallon tank should be cleaned every three days. It is the absolute smallest tank that a betta can be kept in.

Water Change Schedule by Tank Size
Gallons Frequency
1 3 days
2.5 4-5 days
5 7 days

A poor understanding of the nitrogen cycle (the process in which beneficial bacteria are cultured within the aquarium to convert ammonia [toxic] to nitrite [toxic] to nitrate [less toxic]) often leads betta owners to misunderstand how often they have to clean the tank.

Even with a filter, if the tank is not cycled, the betta needs frequent 100% water changes. If the tank is cycled, the betta still needs weekly partial water changes.

Clean water is the best preventative. Medication (such as AquariSol and Melafix) should not be added to the betta's water habitually, as medications can be stressful, and some are easy to overdose.

A pinch of aquarium salt (pre-dissolved in dechlorinated water) can be added with every water change. Indian almond leaf or blackwater extract are also beneficial for bettas (found naturally in their native habitat) and a mild antiseptic.

Live plants can help keep the water parameters stable between changes. Java ferns (Microsorum pteropus), Anubias nana and Java moss (Vesicularia dubyana) are all good, low-light, easy care plants for a betta tank.


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