Some plecos are "specialist" snail eaters... supposedly Scobanicistrus sp. are but... i've never seen it. Loaches are a good bet... but I wouldn't buy any fish with the view it will definately eat the snails in the tank. It can depend very much on the species of snail, and it depends on the individual. No one can say any loach... or any one species of loach are guarenteed to get rid of your snail problem. I have tanks with both clown loaches and yoyo's both ridden with snails. However in the past i have the same species that did eat the snails... so it's a gamble IMO, and if you don't want the fish in the first place... find alternative methods such as putting in cucumber/lettuce in the tank over night and then removing it as all the snails are on it.