This is a good question actually, I dont think I've mentioned it here before. I cant remember what the typical rule of thumb is for clean up crews, something like one snail per gallon. In my seagrass tanks I was keeping just two per ten gallons, and had very little algae to wipe. Astrae and chestnut turbans did very well in these setups. I really dont think you could provide enough microalgae to sustain the typical amounts of snails and possibly the typical numbers of hermits.
>Sarah