mag 9.5 or mag 12

I have a 68g I'm setting up. 36x18x24 and I have both a 9.5 and 12 magdrive return pumps. Not sure which I should use. Only other powerhead will be a mp40.
My return is split with a squid if that makes any difference. Thanks

 

do you know how much the overflow will handle? Im using a 9.5 on my 65g and i have it dialled back a bit with a ball valve. But I also use 3 koralia 2's for additional flow.

 

Its drilled with a 1.5" stand pipe. Not sure what that tops out at gph. A mag 12 seems like a bit much to me tho. I was running a 9.5 on my 90g and it was good. Just double checking.

 

My tank is 36x18x21 57 gal with a 700 gph overflow and 2 1/2 inch returns. I have a Mag 9.5 wide open.

 

I know my overflow would handle a mag 12 because the guy I bought the tank off ran it with one. Just don't know if it would be to much with the mp40 cranking.
Also I'm wondering what the difference in heat added to the water would be between the 2 pumps.

 

Ive tried running my 9.5 wide open and it just blows sand and coral everywhere. thats why I dial it back. I think the 9.5 is plenty flow with that size tank.

 

I would think the 9.5 is plenty for that size tank. I have a 9.5 on my 90 and have it turned down.

 

I have a 9.5 also running my 72 bow..its dialed back and also split to my bio-pellet reactor..

 

I can't help on the heat question but, besides the 9.5 on full I also run one hydor koralia #1 and one #2. My sand moves very little and I have a couple low flow corals on the sand. Hope this helps. FWIW you can always tee the return pump to feed back into the pump chamber with a valve to throttle it back.

 

How big is your sump? You do not want the flow through the sump to be too high or you will have problems with microbubbles since they will not have time to dissipate even with baffles.
I use an Ocean Runner 3500, which is comparable to a 9.5, on a 100G display with a 30 G sump with three baffles in the return section and I wouldn't want any bigger pump.
You will hear 3 to 5x the display volume for sizing a return pump quoted frequently and I feel 5x is plenty if you have other circulation in the display.