When a sump is available, we try to use one.
It allows room for more cleaning machines below the display tank.
The water that passes through the filters will increase and not bother the fish if a 2nd pump is added in the sump.
The processing speed of the water is increased with a simple task of a pump pumping up about 12 inches high, back to the start of the flow.
Cranking up my display pump just made most fish zip away to hide, unless it was a goby or pleco. They like it.
We use sumps for freshwater planted tanks that are heavily stocked with fish.
The fish need the circulation.
The sumps are quite large for more added water volume.
Without the extra 2nd pump, a sump needed a small circulation pump to stop the top-film in the sump.
I figured I'd recirculate upward to the filter instead.
A quiet Sicce pro 1000 (1000gph) 60W max and an Eheim 1692 (900gph)80W max. are used for sump recirculation.
A DC pump is great for the display tank.
These beefy little guys don't use all that wattage to pump 12 inches.
I have heard most pumps use 1/2 the watts just to run though.
The pricey Vectra M1 adjustable DC pump runs hot at high speeds, so we use the DC pump at 1/4.
I can turn it down to feed them or a notch or two up to clean up all the stirred up stuff.
The pumps are such an investment that the one sump is still using a plastic tub.
Really Usefull boxes are tough and work well in a pinch.
Crank up the speed of that sump.
The display tank's DC pump can be adjusted for day/night speeds or simple feeding on a soft mode.
The white EcoTech Vectra M1: 2,100 gph, 80W max (used at 1/4 speed) is the main pump to display.
The Grey Eheim 1692: 900gph, 60W max is pumping back to an assorted stack of foam sponges that I treat like Poret foam.
I smack them out against a wall like a thick car sponge.
Whether the sump box is below or above a display, crank it up!