depends on the tank. some times in large tanks there are fish that eat snails again depends on stocking. another idea is assassin snails that takes some time. the other is cut back on the feedings and use lettuce to bait and remove them. they only reproduce when they have food. the more extra food in the tank the faster they spreed. also they really dont harm anything.
depends what kind of tank but from experiance my girlfriends figure eight puffer when applied to my tank for snail execution duty clearned it out in 4 days and it was over a week before i saw another snail.
if you dont want to add another fish there are chemicals you can add
also you can starve the snails they dont last long without food to starve snails
1. feed your fish lightly make sure it is all eaten
2. next turn on your lights to run 16 hours or so a day this will kick your plants into over drive and grab up more nutrients to starve any alge that will feed you snails
3. no ferts for two weeks lets your plants suck the water dry
That should kill off alot of your snails but keep inmind that you will need to do water changes to deal with all of the rotting corpses (the plants and other snails will utilize that biomass so try to keep this up for atleast two weeks then)
Clown loaches will take care of any snail problem. Several years ago I was in a similar situation as you. I bought 4 clown loaches and within a week I couldn't see any snails. Every once in awhile now, I will find 1 or 2 in my XP3 when I maintenance it......but I never see a snail in my actual tank.
i have an i dea on how to get rid of them i havent tried it yet on my tank because i ordered a newfilter and im waithing for its arrival so i can clean it all out ....first catch all your fish and put them in a bucket ....then take everythink out of your tank .......put gravel in one bucket and decorations in another buket ....then wash your tank with really hot water like from your bath tub ....then the bucket where u have the gravel also fill it up with the hot water and same with the decorations... i am guessing the hot water will kill all the snails in your gravel and your decoration .... oh and make sure u replace ur filter cartridges and clean out your filter thoroughly..... then fill up with all brand new water ......... let me know if it works