What Is This?

I hate for this to be my first post on this forums, but I'm feeling a bit nervous about the state of my guppy.

After cycling a 28l tank for well over a month and all the water parameters indicating its safe to introduce fish, I went to my lfs and purchased three guppies. Everything seemed fine for the first few hours until two of them got a case of swimbladder so in a panic I read somewhere to do a 20% water change and feed the fish some shelled frozen peas. In the morning they seemed to be doing better, not as bloated and swimming around the tank more. Until I saw this.....


What is that?? Or am I just overreacting to a bit of processed pea?

to the forum, patipatspat (great name, btw!).

Sorry to hear you're having problems with your fish. That honestly (although it's hard to be 100% working from a photo) looks like poop!

I would go a little more extreme than the advice you've read; do an almost total water change; leaving just enough in the tank for the fish to swim upright before refilling; don't forget to switch your filter/heater off when doing very big water changes, and make sure the new water is warmed and dechlorinated.

Then don't feed the fish at all for two or three days and see how things look then