I have just bought a tank second hand with fish, it came with 1 clown loach, 1 gourami and a common pleco. The girlfriend has since added 5 rainbow fish and 4 angel fish. Since these fish have been added the pleco has lost it's colour in patches. What could be causing this? I have read that it could be stress from the move or from adding new fish but im unsure and if this is the case how long could it take for him to recover?