Correct! My tank can’t be drilled because it’s tempered glass and filled/set up already and has been. The sump will be 23x17. I will have two reactors, a skimmer, and return pump as well as the heater and ATO. It’s a fowlr tank and currently I have two powerheads. I want to change to a gyre pump in the future. The HOB overflow does have an internal box. Here is a little chart.
As far as HOB overflows goes, the LifeReef is a quality and time tested design.
Your sump is on the smallish side, so high flow can quickly become high noise, as well as high velocity is likely going to carry bubbles through to the return pump.
Likewise, depending operating depth, a larger return pump may draw a vortex.
Other considerations. Every watt of power consumption of a submerged pump (let's not get pedantic about kinetic energy transferred to water or sound, or stored on coral growth, etc.) is a watt of heat into the aquarium.
So 75 gallons + a smallish volume sump means large pumps will cause a more than modest heat gain into the system. It sounds like an external pump is not a likely candidate, so efficient internal pumps are going to be your best bet.
I don't disagree with the other folks regarding recommending a DC pump. I have no experience with Jaebo and have read as much bad as good. I tested some of first DC aquarium before they hit retail market. Every pump that I was sent to test died eventually due to crap electronics. I keep pretty decent tabs on DC pumps and as somebody said above, most come from the same factory or 2 or 3 factories. However, there are some companies that do insist on better electronics packages.
Also (don't want to wade into this here) but "DC" pump is somewhat of a misnomer in this hobby. Some of these pumps are not DC at all, but have an inverter controller running an AC pump on a poor mans frequency drive. Others have the electronics package sealed inside of the pump (less desirable) than those who have the full electronics package built into the controller. When the former dies, the pump is dead, the later means a new controller. It may be moot given the cost for either, but on board electronics packed near the motor windings means more heat and usually a quicker death.
I have had extremely good luck with the ReefOctopus VarioS line of pumps, though I think the standard barrel type coaxial power connector to the control box is a travesty.
The ReefBuilders Nautilus pumps are also rated EXTREMELY well.
So flow: Pushing 900 GPH through that sump may be a bit much, depending on the factors mentioned above and I would assume you end up in the 350-500 gph range.
LifeReef is for the most part 'custom' in the sense that he can/will size your overflow tube(s) to the size return pump that you want to run.
If you want ~800-1000gph the VarioS 8 would be a decent candidate, as it would give you plenty of flow at about 1/3 to 1/2 power. The VarioS 6 would also work, but would likely run at close to full power.
If you want to aim for the 350-600gph then the VarioS 4 would also be ok, but would need to run at 80% power.
I would suggest 2x the VarioS 6 - go with no more than 500gph flow, and use the second pump for the reactor loop and in an emergency it can stand in for the return pump.
