I hope it is alright to post this here; I'm still learning forum mechanics since I am new, and I don't know a whole lot yet about where specific threads should go, but this looks like the right place. If not, please point me in the right direction!
(These are the first fish I've cared for so if I use any terms incorrectly I apologize for that, too.)
I am very worried about my goldfish. I have three of them in an approximately 60 gallon sized tank. I have owned them for about half a year, and I always change their water regularly and feed them what I've seen recommended online (no more than they can consume in 2 minutes time, 2-3 times daily). At first, everything seemed well with them, but recently I've noticed a lot of problems going on in the tank, and I don't know what to do.
It started when I was changing their water about a month ago, and I saw that one of them looked like it had been in a fight. It had a small tear on its back fin and a few tears on the side fins. I'm not sure what exactly they're called so I'm sorry if that's the wrong word to use. I live with my dad, and I called him up to take a look. He said it appeared that one of the other fish was picking on it. We considered separating this fish from the rest, but we can't afford another tank right now and didn't want to move him into what at most would be a small bowl with no filter. We were clueless, and decided to leave him in the tank for now.
I didn't notice any other changes until just today. Today, the same fish that had been looking worse for wear was at the bottom of the tank, not moving much aside from his gills showing he was still alive (thankfully, I was very scared at first) and his mouth gaping open and closed. I had not seen any more injuries previously, and I check my tank at least a few times a day, but today there were more tears than before with barely any of the back fin left, only a small bit. I observed the other two, and one of them has absolutely no marks on him while the other is beginning to look beaten up as well. Much less badly than the other, but still with a few small tears.
I don't know what to do, or what has caused this. I am certain that I am feeding them enough, so I don't think they'd be attacking each other for food. Is it common for something like this to happen, and if so, what is causing it? Is it likely that the uninjured goldfish has been bullying the other two? Please help. I'm very worried about them and don't know what to do.
