You might try your moles in a small tank and only put a few in the primary tank just to see how well they hold up over time. I order (maybe when we retire I can move somewhere I can collect them out my back door ) clams and put a couple in each tank and the rest in a 10 gallon with my shrimp. They seem to do fine and Octane (Hummelincki) has eaten a couple (but not lately). I have lost one in the octo tanks on occassion but my Knobby starfish make sure the tank is not fouled. They seem to live quite a long time this way.