If you are too far north for RES, which is a good possibility, that or they are just plain illegal to stock. You can consider stocking PS(pumpkinseed sunfish). Both species are closely related... PS don't reach the massive sizes RES do, but they will grow to 8"-10" and like RES, have pharyngeal teeth and are capable of crushing snail shells and feeding on them. PS reproduce more readily than RES and can over populate, but they are a viable option for control of snails in northern ponds where RES are not an option. They just need to be managed like BG to make sure they don't overpopulate.
