Second snail sounds like it could be a ramshorn. First is bladder/pond snail like others said.
Get rid of them ASAP unless you want a snail population explosion. Either manual removal, assassin snails or fish that will hunt them (loaches puffers etc) or make a trap. There are some good examples of snail traps kicking around here somewhere.
Or leave them in if you dont mind seeing them all over, which will happen unless they get dealt with when there's only a few.