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My Betta has a big ball on his tail, and is losing coloration, I'm trying to determine the cause, would appreciate some advice.

Luis C

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I bought this really nice imported betta from a reputable fish store, 3 months ago. He’s been great from day one, super interactive, very peaceful, loves to eat! However, last week I noticed a white spec appear near his tail, and over the past few days it’s grown into a lump. He’s also lost a lot of his coloration in about a week, maybe week and a half.

I was wondering if anyone can help me identify what the lump is and how to treat it. Also if the lost in coloration is caused by the lump? He lives in a relatively stress free 15-gal tank.

I used to do water changes every two weeks, but recently I had a filter failure which caused an algae bloom, now I have been doing water changes once or twice a week. I am also 3 days into a black out to fight the staghorn algae that had started to grow. This week the lump has not grown, but his back fin continues to get lighter in color. The first picture is how he looked healthy before any issues. The second picture is from last week. The last three are from today. Behavior wise, he still eats normally, he still as peaceful as always, and he still follows my finger like he always has, so I have not noticed any changes. 

Tank Spec and Water Quality:

Tank size: 14 gal cube

Heater and filter: aqua clear 30 with flow baffle, 75w heater with ink bird temp controller

Tank temperature: set to 80, drops to 77 on really cold days

How long have I had the tank and fish: tank for 4 months, fish for 3 months

Water changes: Every two weeks before, now once-twice a week for 40-50%

Any tankmates?: 7 shrimp and 9 green eye rasbora and 2 nerite snails

Food and amount: bio gold betta pellets about 6-9 of them once a day

Decorations and plants: Fish safe temples, tree shaped driftwood, and many many plants



Ph high range: 7.4

Ammonia: 0ppm

Nitrite: 0 ppm

Nitrate: 10 ppm

Water Temp: 77-80

Hardness: Not sure of the exact numbers, but I live in Los Angeles, CA so its on the harder side

KH/Buffer: I don't know









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Bettas  change colour over time I don't think that anything to worry about the lump could a cyst or tumor and it looks like a some possible fin rot on dorsal fin you could Qarantine try aquarium salt 1 table spoon for 2 gallons for 1 weeks if you have live plant salt at that level is harmful to them

Edited by Colu
Miss spelling
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I agree that his dorsal fin looks strange. It’s hard to tell from the picture exactly what the problem is, but something’s off there.

In terms of the lump, @Kathryn_S recently had a betta with a lump kind of like yours. Here’s that thread: 

In that thread I linked to a video by Foo the Flowerhorn where he actually manually removes his betta’s tumor. It’s kind of intense but it’s an option! 


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Hi! Thank you all for the information it was actually super useful. I took the newest pictures last night to make the post, but this morning the tumor was noticeably bigger. I think I am going to have to attempt to remove it as well. I think maybe I should first treat him for the fin rot, so he is a bit healthier before the removable, and like  @Kathryn_S reported, to weaken the tumor a bit first. I live in the US so I have access to meds. I have Seachem Paraguard so I was wondering if I could treat him with that to not have to remove him from his tank just yet and stress him out, or should I just remove him and treat him with salt in an temporary quarantine tank with a sponge filter and heater?


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