I need to swap these healthy fish.. 1. Male Nimbochromis venustus aka giraffe cichlid. About 17-18cm. Swap to a male blue dolphin of comparable size. 2. Male Nimbochromis livingstonii about 16cm-17cm. Swap to a smaller livingstonii male (about 11-12cm) reason for wanting to swap: these 2 are the biggest fish in my tank, they're stressing the other fish when they fight or chase each other. I prefer a blue dolphin as tank boss because of their more relaxed demeanor.