everybody you guys have to remember head height and pushing against media in canisters. a mag drive 7 will not push 700g at 3 ft. it's rated at 700g at 0ft. canisters are worse because it depends on the media in it. a xp3 will not push 350gph if the canister is on the floor and the top of the tank is 3ft from the floor. all of these pumps and cannisters are rated at 0ft.the higher the return hose the less gph. example my 180gs have sumps and mag 7's as the return pump. from the pumps to the top of the tanks is 4ft the mag 7 pushes 475gph at 4ft.
Canisters are siphons head doesnt come into play some canisters require a minimum height of 24"
I burned one up running it next to a sump
I understand the interest in sump GPH to tank size
But turnover rate of the actual sump makes little sense
If you have 55gal sump during operation only 1/2 at most will be filled
And it still doesnt matter how fast its turning over
If youre interested in the amount of media vs. flow rate sure it matters