I would recommend using non-flaming angles in the future. The smoke and flames tends to get in the way. I particularly like 90 degree angles (non-flaming of course).
Ok, anyway, a flame angel can be kept in a 30g tank, depending on what is currently in there. They like lots of live rock to cruise around and graze on, and can bully certain fish. There is of course a risk of them picking on corals.