If you go with hermits, I would stick with the scarlet-legged ones, and get the smallest you can. Also, keep a supply of empty shells in the tank for them to grow into. This will minimize
the chance of them killing snails. Small scarlet-legged hermits are relatively easy-going.
I'd tend to look more toward the root of the problem though - how are your nitrate/phosphate levels? Algae needs 2 things to survive -- light, and food. Food comes in the shape of 'trates. Using RO