Are the tips white or orange? I'm thinking corynactis.....but if the tips are orange, I'm thinking pseudocorynactis. Pseudos can get large while corynactis average about 1 inch. Corynactis are harmless and pseudos can eat shrim, snails and such.
They are white. There are a few of them, but they don't seem to be multiplying. This one is the largest and it is smaller than a dime. My son has named him spike, so I hope he is a good guy.
Thank you. I am so relieved. My son found it, named it, and thinks it is pretty great. As long as they aren't going to take over they can stay. Thanks so much for your help.