I too acquired some tag alongs on my java moss... There were three surviving ramshorn snails and one pond snail. I did a lot of research to figure out what they were and it turns out that ramshorn snails don't generally eat live plants, rather, they eat all the dead, decaying parts of them. They also eat algae like mad and even that strange crud that forms on the air stone hose. They eat everything undesirable in your tank. Yes, they do poop and they can potentially breed like mad, but the positive side is that they keep the glass and plants looking spectacular! No need to clean the tank, just gravel vacuum!
Their poop is easier for your bio filter to convert, as well. I've had the three ramshorns for over a month and I've only found 5 tiny baby snail specs that I did remove. I'm pretty sure that my peppered Cory is eating all of the eggs in the floating plants and the other cories are getting the ones in the other parts of the tank, so no snail explosion yet. So far I love them as they are fun to watch and they do such a great service!
As for the pond snail, I read they eat plants, so I put it in an unplanted tank. I don't see any babies there at all so far.
Both these snails are hermaphrodites, which is why they can breed so much more prolifically.
I'm not sure what you have there, but if you find it won't eat plants, you will probably find him to be a good friend.
