With snails, they have a HUGE bio load, it is recommended you not have them in anything smaller than a 5 gallon
Actually, I have a 2.5 gallon with shrimp.. and a male betta :)
if you have enough cover and hiding places, the shrimp(s) are more comfortable coming out.... your tank does need a bit more cover (plants) and a hiding spot for your male
hiding spots for shrimp: I use sea shells propped up on a rock... making a little cave, my shrimp actually spend most of their time looking for food or swimming (they are adorable!) they have almost no bio load and help keep the tank cleaner than a snail would in such a small spot
-EDIT-
Snails actually do not eat that much algae, you would need to be wafers for them (special food)