Who Gives A Fish Forums

I've been dealing with this weird issue for a few weeks now - one of my boys has this air bubble thing on his tail. Initially, I was told it's no big deal, but I woke up this morning and it's blown up to like four times its original size.

The weird thing is, he's swimming around just fine and eating normally, so it doesn't seem to be causing him any distress. But seriously, what is this thing?!

- Tank's at 28C
- pH is 7
- Ammonia and nitrite are both 0
- KH is 3, GH is 5

Tank's a year old, fully cycled, and it's a divided tank with two other boys. I do 50% water changes weekly, and I use Tetra Aquasafe on the new water before adding it. I also add alder cones for tannins.

The growth on your boy's tail does seem alarming, but since he's active and feeding, that's a good sign. I'd be inclined to think it might be a tumor or possibly an ulcer, though it's not severe. To be on the safe side, a treatment with Kanaplex could be worth considering, just in case it is an ulcer. However, as long as his behavior remains normal and the growth doesn't increase in size, I'd suggest keeping a close eye on him and maintaining the current routine. You're already doing 50% water changes weekly, but you might want to consider doing them twice a week for extra precaution. And by the way, your boy's colors are stunning.