You can use rainbowfish. They are known to peck at the antennas of snails and stress them to death. The larger ones are more likely to peck at the snails, though.
Snails are good in low numbers to keep excess algae down, but can be a major pest :|
snails are probably the most misunderstood aquarium animal out there. Snails are actually very beneficial to your aquarium. Snails will not seek out to destroy your plants, snails would much rather eat dead leaves / poop, over fresh green leaves. snails are fertilizers. They eat dead leaves / fish poop, and their poop decomposes into the substrate for your plants to consume. A snails bio load is absolutely nothing to worry about. You would need literally thousands of snails in the tank, before there would be a actual problem. If the snails are simply annoying to you, then go ahead and purchase a fish that eats snails or an assassin snail.
Edited: I didn't realize the date on this discussion. My reply is months behind. I'm still leaving it up here though. :-)
I have a few of these snails in my aquarium, only a few that I can see. I suppose there are more. Despite the fact that I consider them water roaches, I do understand that they can be beneficial in controlled numbers. Besides, I have aquatic frogs who will eat them. When I see them and I'm able to pick them out I just snag them and put them in with the frogs. If I squish them inside the tank my guppies feed on the squished snail. I do, as I said, understand that a controlled number can be beneficial to the tank.
loaches i love snails though
I work at a pet store where we get lots of plants in and they always have snails. store. I recently ordered assassinin snails. They eat other snails...pretty cool looking too. I don't have a sale tag up on them...want to see how they do first in our systems. There's an article about them in Aquarium USA 2014 Annual vol. 20. Of course these are the Pesty snails that come on plants. If you want snails but not hundreds of them keep one in a tank. OR NERITE snails are acclimated from salt water and seldom if ever do their eggs hatch. Course they dot everything with them.
Editted: I didn't notice the date on this discussion but I'm still going to leave my comment up here. LOL
As I understand it, one way to control these 'water roaches' is to recognize the source of the problem.
Many times overfeeding the fish can assist in a snail bloom.
Some have suggested getting a snail assassin, however, if you have ANY slow moving life in that tank the snail will make good on its name. There are different fish and this snail you can add, but it may be best to identify the real issue. It may be best to understand the snail and to practice feeding habits that discourage them from thriving and multiplying by the thousands. They may have come in on plants but if you overfeed your fish you could assist in population blooms. It seems like you have reached out for assistance which is a good thing and hopefully you've gotten some sort of idea of how to deal with things.