Well steve out of 3200+ members the problem also happens that posts sometimes get lost. I hate to admit it but it happens. I would like to thank you for bumping this the last time after a few days.
There is no hard fast rule as to how many GPH
"must" flow thru a sump on a tank of a given size. The suggestion of 1
the water flow is a good startign point for the intank circulation of a reef setup. I like a bit more water flow and acutally have my 80 gal
tank setup at 12-15X.
If you want the cleanest tank possible (ie minimal equipment in the display tank) then the sump flow rate will need to process the full flow rate of your system. If you are ok with some supplmental powerheads in your tank then you can have a sump that process's less than the total flow rate within the tank. For example if you wanted close to 900GPH you could size a overflow and a return pump that did that at the specific head pressure you will end up with. maybe a Mag 12 would do the job. Or you could go with a smaller sump return like a mag 9.5 and then add a few medium size powerheads to the tank to get your total flow inside the tank to the desired level.
Overall its good to have approx 5X-7.5X flow rate thru your refuge. So if you have a 10 gal
refuge then shoot for 50-75GPH flow rate thru the fuge. This is if your using the fuge for nutrent export. If you using the fuge for other purposes then the flow rate might need to be higher or lower depending on the conditions. For example if your have a mangrove fuge then you want alot slow flow rate than if your just using it to grow pods
Please also check out our articles if you have not on Refugiums and Sumps.