Yes, but the fish MUST go. NO FISH CAN LIVE IN A 1 GALLON TANK! NOT EVEN A BETTA!! Fish need a minimum of 5 gallons, although some fish, like goldfish, need a minimum of 10 g, but it really depends on the fish. What kind of fish do you have?
All fish NEED TO BE IN A LARGE ENOUGH, cycled, aquarium that HAS A GOOD FILTER and you do a 25% water change weekly. I don't know what fish you have...if it's a betta, upgrade to a 2.5 g, if it's a tetra, livebearer, or cyprinid, then upgrade to a 5 gallon, if it's a goldfish upgrade to a 10 gallon, and if it's neither of those then repost with what kind of fish you have so we can help you choose a more appropriate home for your fish. And to answer your question, yes, a snail can live in a 1g, but it would prefer a 5 g, and since you will be upgrading to a larger tank anyway then put it in that with your fish. Keep in mind that most loaches and catfishes, and also pufferfish, eat snails, so if your fish is one of those don't put a snail in.
Good luck!!!
----fish guy