He is a new cardinal tetra, one of six new ones, and in the bag he would go 'belly up', but then started swimming erratically again. Right now he is in the tank and not schooling with the other five, at first he stopped swimming and was just sucked against the filter, but I broke him free.
What could be the issue? He is staying at the top of the tank.
What could be the issue? He is staying at the top of the tank.