betta with a bump

[frostyowl]

Hi everyone, I'm pretty new to keeping bettas and fish in general, but I've got 3 bettas in a 5.5 gallon tank. One of my tanks was a different 5.5 gallon, and it came with a stronger filter that's supposed to be for 10 gallon tanks, but my fish didn't take to it. I ended up swapping it out for a 3 gallon tank filter, and he seems way happier with that one. I just finished feeding my fish, and I noticed this big bump under his vent area, where his fins are attached. I'm getting a little worried about him, since I've seen some people say this could be a sign of ammonia poisoning or not enough water changes. But his tank is only a week old, and he's swimming around like normal, so I'm thinking maybe the filter is the problem? Any info would be great, thanks.

[frostyowl]

Hi everyone, I'm pretty new to keeping bettas and fish in general, but I've got 3 bettas in a 5.5 gallon tank. One of my tanks was a different 5.5 gallon, and it came with a stronger filter that's supposed to be for 10 gallon tanks, but my fish didn't take to it. I ended up swapping it out for a 3 gallon tank filter, and he seems way happier with that one. I just finished feeding my fish, and I noticed this big bump under his vent area, where his fins are attached. I'm getting a little worried about him, since I've seen some people say this could be a sign of ammonia poisoning or not enough water changes. But his tank is only a week old, and he's swimming around like normal, so I'm thinking maybe the filter is the problem? Any info would be great, thanks.

update: thinking I overfed my betta, could that be the cause of the bump?

[coltin]

Hi and welcome to the forum, I'm glad you're here. If you could post a picture of the fish, that would be really helpful - we'd get a better idea of what's going on.

[goldenfin]

I'm concerned about the setup of your tank, and I think it's crucial we address that first. Three bettas in a 5.5-gallon tank is extremely overstocked. A minimum of 2.5 gallons is recommended for a betta, but ideally, it should be at least 5 gallons, especially if you have plakat bettas.

If your bettas aren't plakats, I strongly advise separating them immediately. If you don't, they'll eventually fight and harm each other. Even female bettas, which can get along, require a minimum of a 20-gallon tank for a sorority setup. You could consider dividing the tank to create separate spaces for each betta, ensuring they each have at least 2.5 gallons.

Regarding the third betta, I recommend getting another 5-gallon or 2.5-gallon tank from your local pet store.

As for the filter, I don't think it's the primary issue here. Unless your betta is getting sucked in or stuck on the intake, the filter shouldn't be causing the problem. A bit of push from the filter might be annoying, but it's unlikely to be the cause of the bump.

It's possible that the bump is a tumor, but if your betta is swimming normally, it's unlikely to be the case. It could also be a case of bloat. If that's the case, I recommend withholding food for a few days and then trying a de-shelled pea after about four days to help ease the bloat.

Please post pictures of your betta, and we can get a better understanding of the situation.