Something strange is happening in my tank!
I bought a 20L tank about 6 weeks ago, so that some of my smaller fish would be safe (I have a larger tank that has 2 pictus catfish with very large mouths...) It was set up in a bit of a hurry so that a siamese fighting fish would have somewhere to go. As a result, it wasn't really cycled properly before fish were added. The tank came with a bottle of stuff that was meant to speed up the cycling process (the bottle said it would be immediate - I was pretty skeptical about that, but used it anyway). I also filled the new tank with water from my established tank.
So after about 3 weeks I had the siamese fighter, 2 albino corys, 2 stripy corys (not sure what they're called!) 6 glass catfish and 4 serpae tetras. I also have an albino bristlenose catfish, a peppermint bristlenose catfish and a gold spot pleco in there - these 3 will be going into the bigger tank as soon as they are big enough to be safe. I came home one day to discover a cory and a glass catfish missing tails and dead. I assumed it was the Siamese fighter as he was charging at the glass catfish. Not wanting anymore deaths, I took him to the fish shop. Yesterday I discovered another dead glass catfish, minus its tail. I watched the fish quite closely, and discovered the serpae tetras doing a fair bit of chasing around the tank - they too have gone back to the fish shop (which I really hate doing, but if they aren't compatible, I'm not happy to let them continue killing my other fish). Anyway, that's not the current problem.
On Thursday I came home to find my albino bristlenose dead, with what looked like internal bleeding (his entire stomach was red). The fish shop told me today they had lost a couple of their bristlenoses too, and couldn't tell me the cause of this, or why my bristlenose appeared to have internal bleeding. They gave me another albino bristlenose, as I only bought that one 3 days before. This afternoon, I have noticed my 2 albino corys have reddish gills, and tonight I've discovered them swimming really erratically and one has a red body towards its tail.
Does anyone have any ideas what this could be? I've tested my water and there is no ammonia, no nitrate, and between 0 and 0.25 ppm nitrite - although this probably means my tank is not cycled, right? I have put some prime in to take care of the possible nitrite, but as there isn't any ammonia in the tank, would it be at all possible that it is ammonia toxicity?
Any help would be appreciated :)