Pond snails will eat your plants. However if you have some algae growing either on the plants or the glass or substrate the plant eating will be minimal. They will mostly feed just on algae as long as there is algae. If the tank becomes algae free they can be APITA! I have to cull mine if the algae getts very low. Another trick you can try if this happens is you can feed them some boiled lettuce , but the penalty for this will be multiplication so culling works the best for me. They do a great job of cutting down algae if problems develop though.
I do not know anything about the reds though. My 2 cents