Return Pump sizing


Reefing newb
Hi all

I am in the process of setting up a 75 gallon Tank
If i remember correctly I should shoot for 10x the gallons for water flow
I believe years ago when I tried to achieve this flow with just the return pump, my sump was like a raging river and i had to downsize the return pump
I have a Mag 9.5 but i think this will be way too much
I also have an eheim 1250 but at 350gph flat, I think this may not be enough
My head height is about 3'

It all depends.

If you run more flow thru the sump, on the return you could install an oscillator and run smaller powerheads.
It is a preference and what corals you have.
Like Mario said it depends a lot on what you are planning on keeping in the tank. I don't like rapids in the sump so I try to keep it around 3-5x in the sump and use powerheads in the display tank to achieve the higher turnover rates.
then maybe i can make the Ehiem work
I would prefer a slower flow in the sump for skimming purposes

The tank will be 3 or 4 fish, softies and hopefully a bubble nem

thanks for the thoughts
This will depend on if you have a built in overflow or your using a hang on u-tube overflow. most hang on overflows depending on size, have a limit that they can handle. Same goes for a built in version. If its a hang on version, what I do with all my tanks that have this type of overflow, is use a larger pump, but put a control valve in line on its way back to the tank. If using a hang on, get things fired up and pay attention to the u-tube. Set your inline control valve so that your flow doesn't allow any bubbles to form at the top of your u-tube. You will than be at your max flow rate. If you want slower flow in the sump, consider getting a filter sock and zip tie it to your drain line. Hope this helps.
Oh, BTW, I'm using a mag 9.5 on my 75 Gallon right now. With about 3' of head. It works perfect. My overflow is a hang on style, rated for 350 GPH.
Thanks DVH
I'm surprised that the 9.5 isn't just sending a raging current through your sump
Anyway, I think im going for the mag 7, The mag 5 im using isn't enough. I do have a built in overflow. I will put a ball valve on the return but I doubt i will need it.