yep, aiptasia
if you just have one use aiptasia x, or cheaper make some paste out of kalkwasser or mrs wages pickling lime mixed with water and inject it over the oral disc in the center, leave the paste on for 45 minuyes or so and suck the nasty thing out with a turkey baster.
Do not try to rip it out or harm it with your hands or tool or it may expel spores and create a larger problem.