We got a flame angel and put him in a 55. He done very well,we took the 55 down to upgrade to a 92 corner so he's in a 29 gal. right now and still doing well. We have ricordias,polyps,leather corals and he's never bothered a thing.Their minimum requirements for a tank is a20 gallons.We have a sargeant major,4- percs,anenome,hermits,snails,crabs,urchin,and a coral banded and they all get along and leave the corals and such alone.There are other angels I like better but they weren't good for our reef tank.