I have a 29gl with a clarkii, 3 striped damsel, yellow tailed damsle, blue chromis, and a green mandarin fish. My tank is fine with 5 fish so I'm sure four fish would be alright and my yellow tailed damsel is a really nice fish. The only one I have a problem with is my 3-striped damsel "Rupert". He tries to beat on new fish but after they have a day or 2 together, hes fine.