I recently bought a nerite snail and it seems fine so far, but he only stays on one main wall. I have brown algae in my tank and he seems to have cleaned most of it on that one wall. the other walls have algae on it and he wont leave that one wall I even took him off and set him down on the substrate but he just went back on the same wall. This seems weird to me because if he can get up why cant he get down or turn the corner? Anyway since there is not much algae on there I don't know how to feed him because he wont come down