One snail always. If there's more than one they run out of algae really fast, even with one snail you'll still run out of algae. So just pick up some algae wafers to feed him after all the algae is gone in your tank.I read zebra snails are good should I buy some if so how many I have small betta girls in a five gallon all together they get along great with each other I due have a back up tank just in case but opinion would help
They may not seem aggressive now but, you should never house two Bettas together (there are some exceptions to this, but I won't go into that).Okay I'm trying to get ahold of a 10th gallon tank for my girls but I'm tight on money as it is