So I bought 8 nudibranchs last month for my tank. My tank is a 33long (48x12x12) and has a severe aiptasia infestation. I have not really seen any changes at all but I do see only 2 of the nudibranchs sometimes at night. They are usually next to each other and have grown a lot. I have not seen any of the rest of them though. For those who have tried this method, did it work for you and how long did it take?