I want to address this on here because I hate these little bastards. They inevitably pop up in almost every tank at some point, and are sometimes a nightmare to get rid of. There are a billion things that people can "squirt" at them to seal the mouths off or melt them or whatever. However, I've found the majority of these methods ineffective at best; such as lemon juice or kalkwasser. Does it kill the Aiptasia? Yeah it does. Then there's a chance a 1000 little pedals will break off and form new ones. Only thing I've ever actually seen that truly works in my life is Lysmata Wurdemanni, also known as Peppermint Shrimp. Problem is that some places try to pass Lysmata Rathbunae off as Lysmata Wurdemanni, even though they're from 2 different areas. Rathbunae tends to have darker almost black tails. Wurdemanni have light, more transparent tails; where the striping of their body is visibly the whole way down. Wurdemannis is the ONLY one that eats Aiptasia. For some odd reason, I guess cost, some people try to pass Rathbunae off as Wurdemanni.