I have 4 fishes in my 75g aquarium. 10in green severum, 9 in golden severum, a 8 in parrot fish and another 12 in cichlid which I do not know what breed it is. I have all these 4 for over 5 years. I don't know what happened recently, the parrot fish started to bully green severum and it's scales were a lot ripped and I see lot of scratches on it's body. It was not able to swim straight and I separated it and the next day it died. It was so sad to see the amazing fish die. Now, the parrot fish started to bully golden severum. I can't separate it completely because the fishes are big and the aquarium is small for the fishes. Next day I released the parrot back again with the other fishes again and it started to fight with golden severum again. I fear it might kill golden too. I am not sure how to contain this situation. Any advise would be highly appreciated. I love all the fishes and do not feel like abandoning anyone.