It's generally regurgitated in the hobby that you need 4x to 10x filter flow in an aquarium filter. I've seen some suggest even more. It's a MYTH!
If you think about it logically, good filtration is about how well we filter water, not how much water we push around through a box. If you were to filter every drop really well, say twice per hour, I'll bet you'd have crystal clear water.
This is very true. I've said in other threads. Did you ever notice the Eheims have much less GPH for the same size tank recommendation as say Fluval and other manufacturers. It's because they believe in the effectiveness of bio-filtration not the speed of it. The 10X turnover thing is from the fish only tanks where you need to remove large waste.
72G - 1 Eheim 2215 - Effective turnover less than 2x
- No Powerheads
46G - 1 Eheim 2213 - Effective turnover less than 2x - No Powerheads