Tetracycline works wonders. You can usually get it from a pet store as a fish medication, but its a general antibiotic that truly works great. The instructions are usually 1 pack per 10 gallons of water, but I'll usually mix a small amount into a gallon jug and just mix it up. When the snakes drink their water they get the medication and most of the times it doesn't take long for them get over the RI.