3 sounds good. Looks like they're buy 2 get 1 free! I bought one of these a couple weeks back for $17 from a local fish store that religiously sells things dirt cheap (giant corporate PS), and have seen them at a couple of other places for $20+. These guys are selling 3 for $10 is pretty crazy. Seems like anyone with BTAs should have a couple of these little guys, they're super cool.