Who Gives A Fish Forums

Inline's cleaner but pricier. I'd only go that route if you're setting up a new canister. Retrofit kits exist, but they're finicky with hose diameters. What's your canister's output size? My Fluval 306 needed adapters for a 3/4 inch UV unit.

What's your current flow rate on the 407? UV units usually need a slower flow to work right. I tried one on my Rena Filstar but had to dial it back to like 150 gph. Also, keep an eye on bulb life, they lose effectiveness after 6–8 months.