Recently bought 4 threadfin rainbowfish for my 23l tank, which had been established for 2 months previously, with 2 otos and 8 cherry shrimps living happily for well over a month. I aclimatised them properly, floating the bags, transferring water, keeping lights off, no food, etc. As soon as they were in the tank one was having trouble swimming, it kept sinking and want using it's tail fin at all. It died within a few hours. The next morning I woke up to another dead one, who hadn't shown any symptoms. 2 days later and the other two seem to be healthy, however one is always chasing the other, especially when feeding. They are all male. My water perameters are all normal according to my test kit, ammonia and nitrite at 0, nitrate at 15-25.
Does anyone know why the two could have died so early and how I can stop them from being so aggressive now?
Does anyone know why the two could have died so early and how I can stop them from being so aggressive now?
