Help!! Betta with large separation to fin and body

  • #1
I have no idea what is going with Pearl. I have had her for a year, since she was a baby. She has been very healthy her whole life. She is the only fish in a 5.5 gallon aquarium. She has been acting normal since I cleaned her tank last weekend. Thursday, though, I noticed she was lethargic. Last night (Friday) as I was feeding her (she’s still interested in her food), I discovered a very big separation in her fin and body. Here is the information and a photo. Please help me figure out what is going on with her and anything I might try doing to help her. I’m very worried about her!


What is the water volume of the tank? 5.5 gallons
How long has the tank been running? About 15 months
Does it have a filter? Yes
Does it have a heater? Yes
What is the water temperature? 78.9
What is the entire stocking of this tank? (Please list all fish and inverts.) 1 betta

How often do you change the water? Weekly
How much of the water do you change? 10-15%
What do you use to treat your water? Tetra conditioner with our tap water. We have very hard tap water so I combine the water so condition with some TopFin preconditioned aquarium water.
Do you vacuum the substrate or just the water? Vacuum the substrate every other week and change the water weekly.

*Parameters - Very Important
Did you cycle your tank before adding fish? Yes
What do you use to test the water? Tetra Easy Strips
What are your parameters? We need to know the exact numbers, not just “fine” or “safe”.
Ammonia: 0
Nitrite: 0
Nitrate: 0
pH: 7.3

How often do you feed your fish? Usually twice a day. Sometimes I mix it up and only feed once. Usually I feed 3-4 mini pellets twice a day.
How much do you feed your fish? 3-4 mini pellets twice daily. Note: these are the mini pellets for any size fish, not the larger pellets! I have had this betta since she was a baby and could only eat the very small pellets. She resisted the larger pellets so I have continued to feed these to her.
What brand of food do you feed your fish? betta bio gold
Do you feed frozen or freeze-dried foods? No

Illness & Symptoms
How long have you had this fish? 1 year
How long ago did you first notice these symptoms? Thursday I noticed she was lethargic. Friday evening I noticed the large separation in her fin and body. Prior to this she was behaving normally and looked healthy.
In a few words, can you explain the symptoms? Became lethargic (resting on the bottom of the tank) on Thursday. On Friday evening, I noticed the huge separation in her fin and body.
Have you started any treatment for the illness? No
Was your fish physically ill or injured upon purchase? No
How has its behavior and appearance changed, if at all? Yes! See my answers above and see my photo for reference

Explain your emergency situation in detail. (Please give a clear explanation of what is going on, include details from the beginning of the illness leading up to now)

I have had Pearl for a year. She was a baby when I got her. She has always been very healthy. She is the only fish in her tank. She was behaving normally and swimming all over her tank for the most part of the week. On Thursday I noticed she was lethargic. She was resting on the bottom of her tank a lot and not swimming or behaving like usual. Friday evening (yesterday), I noticed she has a very large separation to her fin and body. She is still interested in eating but spends the rest of her time at the bottom of her tank.

I do not think this is fin rot. Her fins were healthy early in the week. This was very sudden and dramatic. I am familiar with fin rot. I have another betta in a different tank who had fin rot about a year ago. It was a very gradual onset. I was able to treat it successfully, and his fins have regrown and look beautiful again.

I would appreciate any ideas on what is going on with her, what I could try doing, and whether or not it seems likely she will make it. I am so worried about her!


  • #2
Well that is certainly very strange. I wonder if her tail got stuck in the filter intake? You may want to get a sponge for that. Has the body always been dented like that?

  • #3
So this looks like fin rot to me. I circled the part in the image where her fin is gone, deteriorated from the rot. It doesn’t look like an injury like a tear from decorations, and it doesn’t look like she’s fin nipping herself either. Best guess is fin rot. It’s not too bad, so daily water changes (50%) should work. You can also add aquarium salt if you want, and indian almond leaves for the tannins. If it gets severe later on you can do meds like api fin and body, but she isn’t to that point yet. My own boy is suffering from fin rot, it’s no fun

To prevent this in the future i would do larger water changes (50% weekly). I’m also curious as to why you have 0 nitrates in a cycled tank. Do you have real plants?


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  • #4
She might have been torn in the filter, and then gotten infected either way.
  • Thread Starter
  • #5
Thanks for the replies. Yes, the end of her fin looks like it could be fin rot, I agree. I’ve successfully treated another betta for it in the past and will begin the aquarium salt and daily water changes ASAP. I only change about 15% because I do it weekly. I find with a smaller tank, I don’t need a larger water change as the quality of the water is fine with a smaller water change. I do more like 20-25% every other week when I clean the tank.

the part I’m worried about is the very large separation to her fin that extends into her body. It was not like that last weekend! If that is fin rot, it’s really, really severe and happened very suddenly. In my past experience with fin rot, it was more gradual. My other betta had fin rot about a year ago. At first I thought he had scraped himself against something in the tank, but it progressed over the next week and he became somewhat lethargic and not himself. I began doing daily water changes with aquarium salt, and he has since made a full recovery with beautiful regrow of his fins.

I can’t say why I have 0 nitrates. It’s not a planted aquarium. Possibly it’s slightly higher than that but not enough to pick up on thetest strip I’m using.

Here is a photo of Pearl before she was sick.


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  • #6
Tail Biting?


  • #7
That does look like an injury to me. Maybe the filter or the heater. It doesn't look like that huge hole in her body stems from fin rot or fin biting.
I would do daily to every second day water changes of at least 50% and see how she does and add IAL.
Your nitrates might be higher. I find the test strips very inaccurate and unreliable.
  • #8
Whether it’s fin rot or a tear the recommendation is the same: water changes, salt and tannins. But if others think this could be from a filter it might be good to look into a different safer filter, or figure out how to fix this current one
  • Thread Starter
  • #9
Thanks for helping me. I have already done a water change of 50% with aquarium salt. I’ve used these kinds of heater and filters for years with no problem. She likes her heater a lot and sleeps near it so I think it is possible she could have injured herself on it. It’s so strange. I’m going to look into different heaters and possibly a different filter.
  • Thread Starter
  • #10
A little update. Since I changed Pearl’s water and added aquarium salt earlier, she’s acting like she feels a bit better. She’s swimming around more than she has the past 48 hours. Not a lot, but it’s an improvement.

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