yes they are aptasia
same my peppermint shrimp didnt do any thing. well if the rock is light and near the top of the tank then heat up a soldering iron and take the rock out the water, and hit the aptasia with the soldering iron. it does smell a bit at ther size they shouldnt smell that much. or if the rock is big and heavy then buy some joes juice im getting some of that soon. people have said it is very good. you can get it from here http/www.coralculture.co.uk/shop/advanced_search_result.php?keywords=joes+juice&osCsid=bo31qglgoeuid2gejl56u8m5h7 it also has lots of info on that site also you can get it from ebay
Don't try to remove it with tweezers, You'll just remove part of it, and it will regenerate, and possibly spread, and it will also withdraw into a little crack or hole in the rock, and essentially you'll do little to no damage to it, and you'll possibly help it spread.
As seffie would say, get a soldering iron, and burn the little !
well when you take the rock out the aptasia gos in a bit but you can see its head sticking out. just hit it and it will go in its hole. i dont know if it dones decompose? it might but it shouldnt afected your water if it dones.
just be careful not to squirt too much juice on them, or do it in stages if you have alot of them. I forget what the main ingrediment in joe's juice is, but it could change params in such a small tank (pH fluctuation maybe)