I ve 6 fishes in my aquarium 2 of them have become lazy, I think they are sick.......... even they can't swim more then 2-3 min. and after this they get tired and lays down.......... I ve heard that there is some kind of capsule available in the market for the fishes which we ve to mix in the water of the fish tank.......... is that true and if we use that capsule it may affect other fishes too....?????

plz reply fast..........