In my 500 I have peppermint shrimp that I hardly see with all the rocks but they do a good job. If Aptaisia is within reach and I feel energetic I inject it with a thick solution of Kalkwasser or pickling lime and that usually does a better job than the wand zapper I bought and was not successful in using it effectively on Aptaisia. Using the wand to kill blue star polyps that are spreading..