Most Loaches will eat any snail, big or small! They can even devour an Apple snail by eating the breathing tube and suffocating it, then eating the rest of it. Disgusting though.
But depending on the size tank, I'd reccomend Angelicus Loaches, as mine totally cleaned a tank full of snails in a matter of days.

If you have a smaller tank, My Dwarf Loaches seem to have done a good job too. Avoid Yoyos and Clowns if you have a small tank though, as both can reach 8" and over. If you want your Loach to be a long time member (Can't think of why you wouldn't, but hey) then Clowns and Yoyos are a no. Also, stay away from Skunks as they can be very aggressive. I could go on about the ones NOT to get for a while, but you may not even see these at your fish store. Best thing to do would be to go there, look at what Loaches they have, then post back. And research them.
I suppose a Goldfish could be okay....but I'd personally still be wary. And you'd have to deal with the quarantine of them for a couple of weeks before you could even put them in your tank. Though I suppose it'd be the same for the Loaches.
And actually, some fish can be sensitive to water temperature...they can keel over and die. I've had Platies die because my heater broke when I was on vacation and the water went down to 65. I agree though, most fish should be able to handle some temperature difference.

These ones very also very close to giving birth, so it may have been stress and birthing troubles.
If you do get the goldfish for your tank, and they are kept in coldwater at your fish store, make sure to acclimate them slowly to higher temperatures. You don't want them to be very shocked and stressed, and get ich, or another disease, or just plain die.
I just realized, we are going on about how to clear the tank of snails and the original poster hasn't even said it's a problem yet. Oops.

Though chances are, if you have one snail, you'll get more. Snails breed like crazy, and even though you only see one, more may be lurking around in the substrate, or hiding in plants. Also, you could have gotten eggs on your plant, so you'll have lots of little snail babies. Some snails are okay, as some kinds will turn over sand, and eat alage, but some are just pains. If you don't want snails, then take this one out, or get one of the fish suggested.
Anyway, I'll shut up now....tell me if this post makes no sense, because I'm just kind of blabbering. Heh...really am going to shut up now.

)