there are shrimp that will eat the small aptasia (Aptasia Shrimp) they are primarily red in color. However, there is a product out that i used to use when i had a reef tank. it comes with a plastic syringe (the med. is kind of green color). you fill the syringe and literally inject the apitasia with the med. it worked pretty good for me. the only thing is that you don't want to wait too long because they spead rapidly and the injection thing could end up being an all day process. i am assuming that you have a reef...if you have a fish only the shrimp will be eaten!!!