I'm With Bang GUy, They shouldn't be on sale, But for advise make sure you tank is at least 100 gallons with LOTS of live rock and a very good amount of swimming room, there algea grazers, and I don't think they eat seaweed sheets, so maybe you'll end up having to buy live rock every week for its food?
Thats what my neighbor does, He's has only been around for 3 months.