I've also heard them referred to as strawberry anemone. I have a few in my tank and they are definetly harmless.

harmless and kinda cute.i have a few in behind some rocks.

up to how big they grow ?

I shouldve been more descriptive when I said take out and run under hotwater and if it fails scrub with tooth brush in your sink... But since you have many more in your tank manual removal may be harder.

If you try to scrub anything in your tank you could definitely create more problems or even kill other corals in your tank, don't scrub anything other than algae off the glass in your tank, always remove and scrub in sink.....

thanks for letting me know about brushing
i brushed aptisia in my tank it was all over