After adding some plants to a tank, I suddenly have a small army of snails. I'm not too upset (yet) because there was a fair amount of algae and they seem to be helping, but I would like to know what kinds they are. The first one is the same shape as my nerite - round with a point on one end. The second one is flat and spiral-shaped. (They're kind of hard to see in the pictures, especially the second one.) Thanks for any info you can provide!