Apple snails are the one type of critter I deliberately allow in the hatching tank with my cories. In fact I hatched my last 12 broods of apple snails in there between 2 sets of cory fry.
I am interested in the idea of rams horn snails killing apple snails, because I'm not sure that's what happened to my big ones, but I've been suspicios of them and the pond snails. my rams horns are out of control worse than the pond snails in every tank. I pick them out and give them to my brother in a little critter keeper with a bit of greenery to feed his puffers. They like them. I allow a few rams horn in my goldfish tank and sometimes sit there for about half ann hour at a time picking out all the unwanted snails that have managed to hatch in my fry tank and tossing them in the goldfish tank, where they eat most, but there are a few bigger live ones. They manage to get eggs everywhere and they hitch rides with cory eggs from the comunity and grow up fast enough to lay more eggs pretty quick. Last time I fed snails to the goldfish I got out all the pesty ones that were as big as my latest generation of baby ivory apples, so maybe it's almost under control there. I have even fewer trumpet snails, but they are increasing since I've reduced my overfeeding habbits and have my tanks well enough ballanced so I don't have to vacuum the gravel as much. I haven't allowed apple snails in with other snails on pupose since I lost an entire generation pretty fast. i thought it was mostly acid water and low calcium, but maybe all those litttle pesties crwling on their shells were helping erode them. i don't find apple snails to be too messy if they're not over fed. They barely need more than what the fish in the same tank need, especially if you have algae growing on stuff, but they do love to eat almost anthing I put in, especially algae wafers. I haven't observed they much with shrimp, but at tthe store where I got my first apple snail, they were being eaten alive by little blue lobster guys in the same tank.
.
