When I bought my place I used to have thousands of tiny snails on the shore line they weren't round shape like the trap door snail they kind of conical shape. I have stocked RES and I haven't seen as many the last couple of years. I have caught fish that have the black specks in the meat and also the white little grubs. I haven't seen as much in the fish meat lately. My cousin in Florida has a KOi pond with these trap door snails as big as my fist. His wife got them from some Asian restaurant. I would like to have a few of them but I don't know if they would make it here in Indiana