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Fish/Betta fish fin rot/fin loss


Hi Richard,

I have a Betta fish named Patrick. He's kept in a 2.5 gallon tank with a Tetra Whisper 10i filter, a heater, and a little ship that he can swim in and out of. I've had him since July and do water changes biweekly with Tetra Aquasafe Plus.

About a week ago, I started having trouble keeping the modem on the bottom of the filter. After a week of failed attempts at removing and fixing the problem, I decided to remove the filter completely. At that point I did a partial water change. However, two days later, I noticed Patrick's top fin was completely missing; it was laying next to the ship.

I know all this info might be irrelevant, but I'm unsure whether the filter removal and water changes could have led to fin rot or if he ripped it on the ship decor. Regardless, I'm unsure if there is any difference in treatment between fin rot and fin loss. I took out the ship and did an 80% water change, but what should my next steps be? How often should I now be changing the water?

Thanks for all your help!

Hi Alyssa

My guess is he broke his fin on décor in the tank. His other fins look healthy so I don't think it is fin rot. Along with taking the ship out, make sure there is nothing else in the tank that can tear his fins (no sharp rocks, no plastic plants etc) In my Betta tanks, I only use live plants and I build caves for the fish using polished rocks that won't tear the fins.

You'll need to replace the filter, but I would use this opportunity to upgrade his tank to a 5 gallon with a hang on back power filter. Your heater for the 2.5 gallon should be enough for a 5 gallon. However, you can get 5 gallon kits that come with everything you need (except decorations) at Petco, Petsmart for about $40.

Regardless of the tank size and filter, fish need a 20-25% water change each week.

His fin should grow back in time. I would get some Pimafix and follow the directions on the bottle. This should prevent infection etc along with 1tsp of aquarium salt.

Please feel free to contact me should you have any additional questions or concerns.

Hope this helps you, good luck!



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Richard Hight


I own and maintain several freshwater aquariums from 2 to 180 gallon. I can answer most questions about freshwater aquariums, including setup, cycling, maintenance, compatible tank mates, feeding. Moving? I've moved fish both across town and across the country and can help you get your little aquatic friends to their new home safely. I know and have experience with most freshwater community fish, South American Cichlids and African Cichlids. I don't answer questions about Goldfish or keeping Goldfish with Tropical Fish. I also don't answer questions about keeping crustaceans (shrimp, snails, crabs etc) with Tropical Fish, nor questions about saltwater fish or aquariums. I'm not available to answer questions on weekends, this is when I do maintenance on my own tanks.


Many years of personal experience with fish and aquariums

HSG 2010-2011 prof

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