WTB canister filter
 

need something that pumps 300-400 GPH

Why 300 GPH? Hate to tell you this but you're screwed, you are looking at a Fluval FX5, a Rena XP4 (marginal) or an Eheim pro3 none of which are cheap. I fyou need that kind of turnover for mechanical filtration in FW get a couple of AC110s and be done with it. If it's for a SW tank I'd say you are probably over estimating the required canister flow unless you are talking about a 75 gal plus. You'd be better off to go with a Fluval 405 ish canister and use powerheads to make up for the lower flow rate. That isn't really an optimal solution though, you'd be far better off with a sump.

nope its for a ten gallon nano, and i want it to produce enough flow so i dont need a powerhead