My flame never bothers any corals but is semi aggressive to other fish. 20 would due for a small one but ultimately you will need to upsize. I have zoas paly xenia softies frogspawn hammer few acros btas.I am working on getting a 125 gallon reef tank, but I was told that flame angels will eat the coral. I decided to stay away from it even though it is my favorite fish. Since I really want one, would it be possible to keep it by itself in a 20 gallon I have set up. Or does it need bigger? I was referred here from r/reeftank on reddit with this question