Ok, but how do I know if I have one or not. I removed all the rock, place it on a table and inspected all the holes and crevices: NOTHING, and I used a long stick to dig into the holes, I don't want to shake hands with a mantis. I found nothing, but yet I still hearing the sound. I will get a shrimp gobby any way. But once ahain how do I know what I have? Aldo any suggestions about pepermint shrimp to get rid off aiptasia in a reef tank with a bubble coral, Torch coral, stra polyps and zoo's?