Actually.. if it's already been in your tank, i wouldn't bring them back. You could possibly introduce something back in to the ocean when you return them that may be bad for the ecosystem. I'd say your stuck with them. Either let them die in your tank.. try and feed them, or just take them out of your tank and kill them so you don't have a spike in ammonia from the decaying snails. Please don't bring them back to the ocean though.. that would be very irresponsible. Almost as irresponsible as taking them back to your tank in the first place.
My bad....zer0 is absolutely correct here!!!!Actually.. if it's already been in your tank, i wouldn't bring them back. You could possibly introduce something back in to the ocean when you return them that may be bad for the ecosystem. I'd say your stuck with them. Either let them die in your tank.. try and feed them, or just take them out of your tank and kill them so you don't have a spike in ammonia from the decaying snails. Please don't bring them back to the ocean though.. that would be very irresponsible. Almost as irresponsible as taking them back to your tank in the first place.