Scats and mono's used to be a very common fish and I had them from when my reef was brackish water as they will live in that and full salt. Mono's especially are probably the most hardy fish and you can't kill them unless you lay them on the street and have a school bus loaded with 60 overweight kids run it over, twice.
They will eat anything and get quite large, like 7". Mono's also live in brackish water and are almost as hardy.
I don't remember if they eat aiptasia as I didn't have any then.