1st your snail does not eat its own waste, so start the filter. You need to feed it occasionally, an algae wafer, some rommaine lettuce, spinach, something.
Alot of snails don't need heat, they will survive nicely at room temp, though 55 is a little low, aren't you cold??
I have only been able to find the 25 watt heaters online at petwarehouse.com