I am new to discus keeping. Recently I bought 2 discus to try out. After 2 weeks, one of them became black and died. This discus was the more active of the two. Then I bought another 2
discus last week and one of them has become black but not dead yet. Looks like it’s not going to last. Why do these fish become black and died?
You must quarantine your new fish before you introduce them into the tank.
Otherwise either your fish or the new fish will get sick.
Put your new fish in a separate tank. Treat them with Formal in solution (35%-40%): 1ml to 2ml to 100 liters of water. Change water and apply same treatment for three days.