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Betta Fish Fin Rot: Symptoms, Causes & Treatments

Lindsey Stanton Profile Picture

By Lindsey Stanton

betta fish fin loss

One of the worst things a betta fish owner can witness happening to their betta’s beautiful long fins is to watch pieces of them waste away. This tragic illness is known as fin rot. Just as the name implies, the fin begins to rot away in small amounts over a short period. Fin rot is common amongst all types of betta fish and can easily be cured with the right medication and care.

If you notice that your bettas tail is not looking how it used to, this article can help you!

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Fin Rot Explained

Fin rot is caused by an infection that slowly begins to eat away at the betta’s fins. This results in the fins looking ragged and torn. It will appear as if your betta’s fins have been through a blender. This is usually caused by a gram-negative bacteria or fungal infection, which is prevalent in betta fish.

The fins also begin to melt, and it will seem like bits of the fins are fading away, which leaves uneven and ragged fins. Every betta owner will deal with this illness sometime in their life, and luckily it has a high success rate, and most healthy bettas can easily overcome this illness.

crowntail betta fish
Image Credit: ivabalk, Pixabay

Tail Biting or Fin Rot?

Both tail biting and fin rot look identical. However, they are truthfully quite different in terms of treatment and causes. Tail biting is a self-destructive behavior brought on by stress and boredom in bettas, but fin rot is controlled by pathogens that eat away at fins without the betta’s involvement.

These two issues are equally serious, but treatment varies. For instance, stress that leads to tail biting should be addressed by finding the root of the issue, whether it is caused by a small tank or strong flowing filters. Many people will witness their betta biting their tail and see bite-sized marks towards the ends of the fins, which makes it easy to diagnose. Tail biting can make the fins more susceptible to bacteria and fungus that can cause a form of fin rot.

Sometimes incompatible tank mats will nip the fins of your betta, which can give them a ragged appearance. Always monitor the behavior of certain fish if you add them to your betta’s tank.

close up betta fish
Image Credit: Icewall42, Pixabay


Determining if your betta has fin rot is the first step to a successful treatment. Keep in mind your betta may not show all the symptoms, but if you notice most of the symptoms are showing up on your betta fish, they are likely suffering from either a mild or severe case of fin rot.

  • Ragged fins
  • Holes in fins
  • Tears
  • Dangling pieces of tail flesh
  • Lethargy
  • Bottom sitting
  • Loss of appetite
  • Necrosis of the dead skin
  • White film at the ends of the fins (new growth)
  • Visible blood vessels
betta fish tank
Image Credit: Kosit Pajuthai, Shutterstock

The 5 Causes of Fin Rot in Bettas

1. Bacterial infection

This is the most common cause of fin rot and is from a gram-negative bacterium that is present in the water column. This bacteria can enter the smallest wound on a betta and become severe if not treated properly.

2. Fungal infection

This is a less common reason that causes fin rot, but the white fluffy growths accompanied by a fungus infection can cause a mild case of fin melting that mimics fin rot symptoms.

3. Dirty water

It is no surprise that dirty water hosts a variety of disease-causing bacteria. If your tank is dirty and cloudy with regular algae blooms, your betta is susceptible to bacteria that will eat away at their fins. Bettas need a filter and a fully cycled tank. Regular water changes should also be done to keep the tank clean.

4. Small aquaria

Small tanks cause stress and allow the water to rapidly become toxic from high levels of ammonia from fish waste. Bowls, vases, and tanks under 5 gallons are unsuitable for bettas and can quickly poison a fish in its waste. Fin melting is common from the burns sustained from the toxins in the water.

5. Physical damage

Bettas can sustain injuries from rough decorations and fake plants, as well as getting stuck in a filter or as a result of fin nipping.

crowntail betta_Lyudamilla_Shutterstock

Image Credit: Lyudamilla, Shutterstock

Effective Treatments for fin rot

These medications seem to have the best healing ability for a betta with fin rot. There are two stages to treatment that contain different medications. Here is a thorough treatment list to help your betta successfully heal from their ailments.

Stage 1: Medicate
crowntail betta
Image Credit: Arvilla, Shutterstock

Preventing Fin Rot in Bettas

Fin rot can easily be prevented by providing your betta fish with the right tank conditions. Bettas should be kept in a fully cycled tank (established beneficial bacteria from the nitrogen cycle) that is over 5 gallons. However, a 10- to 20-gallon tank is better long-term. The tank should have a filter and heater to keep the conditions ideal. A 30% water change should be done weekly to remove toxins that build up in the water. You can also place 1% of aquarium salt in the water to promote your betta’s slime coat naturally. Water additives can be placed in the water to keep the overall water clean and free of harmful bacteria and fungi. Bettas should only have live or silicone plants in their tank to prevent rough decorations from snagging and tearing their fins. Always make sure the filter is not strong enough to suck in your betta, as they are generally quite poor swimmers.

Related Read: Do Betta Fins Grow Back?

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A healthy betta can easily withstand major symptoms associated with fin rot and survive treatment and the healing process. Bettas are quite hardy and should rarely fall ill if they are fed a good diet, have an appropriate tank with the necessary equipment, and have their water changed regularly to keep the ammonia and nitrate down.

We hope this article has helped you to diagnose, treat, and prevent fin rot in your betta fish!

Featured Image Credit: Wirestock Creators, Shutterstock

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