My golden mystery snail has alot of green on its shell. It has really grown quite large and lost a lot of its original color-the algae definitely doesn't help. How long can it be comfortable out of water (if at all)?
They can actually be out of the water with no ill effects for a couple of weeks, so cleaning the shell would not be an issue. I even ship my snails out of water in damp polyfill. I would use a brand new soft toothbrush to clean off the algae. Mine are also getting "green" now that they are no longer with shrimp to clean their shells.