I bought a scooter blennie 2 weeks ago for my 3 year old 75 gallon tank. I have a refgium and checked to make sure it was teeming with pods and it looked like it had the proper microbiome to support the fish. He did excellent for two weeks. Exaclty two weeks later he went missing. In between them I added an emeral crab, can they feed on the microfauna of a tank?