Hiding Nerite Snails

Nov 13, 2012
I have 6 leopard nerite snails and 6 zebra nerite snails in my aquarium as a clean up crew. Generally I see the zebra nerites doing their job but rarely see the leopard snails out and about. They stay inside the artificial driftwood and I never see them roaming the aquarium. From everything I read these guys are supposed to be algae seekers and destroyers. Does anyone have any expericence and information regarding these snails. I just don't get why they aren't out and about cleaning the algae and are content with being inside the driftwood. When I look inside the driftwood, I don't see a presence of algae to where it looks like a continual food source is present. Thanks.