Fluval filter numbers?

[Airborne 82nd]

Help with fluval numbers on the FX4 it says pump output is 700gph below that it states filter circulation is 450gph. What is the difference? If it pumps out 700 it seems like it would also take in 700 so it would circulate 700. If it pumps out more than it takes in the tank would overflow. I know there is something I'm missing.

[face]

The pump can do 700 but when it’s going through the filter it’s only 450 I think is what it’s saying 

[Pepere]

Filter media imposes a flow restriction.  Pumps are typically rated at zero head loss.

 

 

[Airborne 82nd]

I understand about the load. They are all rated with NO load because the manufactuers have no idea what you are going to put inside or how clogged up you will let it get I get that. So if it gets half way stopped up now the intake can only take in half the water it did but some how it can put out more than it takes in. I think I get the max output of 700gph not sure what they are saying about the 450gph circulation and how or if they compare.

Thanks for the replies. But I need more some fluid flow type of engineer that can explain it to a dumb old country boy😕

Airborne

[Dacotua]

If you put only bio media (no sponges) in a filter, it will flow more. Sponges will restrict your flow and the more clogged they get, the more they restrict it.