What size return pump for maximum flow?

[NHLIVES]

I have ordered an All-Glass 120 Gal MegFlow. It comes with two overflows each rated at 600 gph (using a 2400 gph pump at a 5 ft. head).

To get 2400 gph out of a Mag-Drive (for instance), you would probably need roughly two Mag-Drive 3600's (accounting for ball values, etc.).

Does this make sense? To get a 10x flow through the sump, you would need to drive the overflows at a maximum flow. Do you need 10x?

It all seems a bit much for me.

Rob, a really good podcast topic. There are many posts on this topic all of which simply (or mostly add to the confusion). IMHO

[gwen_o_lyn]

I don't know too much about overflows and hooking all that up, but either way, you won't have enuff flow just coming from the returns.

I don't think your overflow kit will handle 2 mag 36's. That's 3050 gph each with a 5' head if we are on the same page. You may have to really dial it down, and that may not be worth the extra electricity.

Anyway you do it, consider adding a few tunzes to the display.

[NHLIVES]

So I just found the pointer to the calcalators on Reefcentral.com. Assuming I used it correctly, I would need a single Mag24 to drive the sump at 10x. Does that sound right? It certainly makes more sense.

And I know I need additional flow via powerheads to ramp the total flow to maybe 50x. Thanks Gwen for the reminder though.

[gwen_o_lyn]

Just curious, why so much concern about the flow in the sump? Is it going to be a fuge too?

[NHLIVES]

Yes, there is a fuge. As to the 10x, it was suggested by a "mentor" and I think I have seen the the number in various other forums as a target. If that is not correct, then all bets are off.

Also, would it be better to have two smaller pumps? Failure of one would not completely halt flow through the sump. Using the Reefcentral calculator, it seems that two Mag9's deliver the same flow as one Mag24 making the smaller pumps somehow more efficient.

[George]

My 2 cents:

There has been talk about decreasing flow to the sump so that sump based skimmers have more dwell time with the water, skimming it more, thus returning less organic laden water to the tank than blasting water through the sump at maximum capacity provides. Use circulation pumps like Tunze or Seio to provide motion in the tank. The added bonus is the smaller return pumps are cheaper and add less heat to your tank.

I was under the impression that fuges wanted lower flow, but I'm not an expert on fuges at all, so those who know more, please correct.

Overflows accumulate gunk just like everything else in the tank and are ripe spots for hair algae and coraline algae. Any of these can reduce flow capacity slightly to drastically. Running the overflow at max will be asking for a flood as that buildup occurs.

Since you have 2 returns, I'd say yes, it's better to have 2 pumps. They're less costly, a failure, as you mentioned, is only a 50% loss. They would be much more flexible on flow management as well.

[Rob]

yes, great topic, i think this is something im going to have to revisit in the future...
in a sump it doesn't matter, they dont do anything but increase water volume
you may choose to decrease flow to give your skimmer more time with the water, but i think the overall value of this is marginal. with a fuge its a different story. depending on what you have in the fuge you really only want about 5-10x flow max in there. otherwise it may not be able to do what you need it to do (although what that is depend son what you are trying to do)

[lReef lKeeper]

the 10x turnover is a bit dated, imo. i have read in many forums that you should try to shoot for about 40x turnover. this can be accomplished with a closed loop system, and an extra pump in the return portion af the sump or a few powerheads in the tank. i really think you should look into the closed loop, as you know the whole "flow" thing is, in part, to get food to the corals.

you can also open up your stock returns and switch them over to drains also. i have all four bulheads in my overflows draining to the sump and a closed loop with a mag 18, and a mag 9.5 for a dual return in my 125. the return is a seperate set-up than the return line.

[DEdwards]

Not sure if this helps on your calculations or not. It's a chart of the Mag-Drive's at various head pressures. If it doesn't help then just ignore me.

Danner Supreme Mag-Drive Aquarium Water Pump/Powerhead - Marine Depot - Marine and Reef Aquarium Super Store (http://www.marinedepot.com/aquarium_powerheads_pumps_danner_mag_drive_supreme .asp?CartId=)

[NHLIVES]

you can also open up your stock returns and switch them over to drains also.

Interesting...

[Rob]

the 10x turnover is a bit dated, imo. i have read in many forums that you should try to shoot for about 40x turnover. this can be accomplished with a closed loop system, and an extra pump in the return portion af the sump or a few powerheads in the tank. i really think you should look into the closed loop, as you know the whole "flow" thing is, in part, to get food to the corals.

you can also open up your stock returns and switch them over to drains also. i have all four bulheads in my overflows draining to the sump and a closed loop with a mag 18, and a mag 9.5 for a dual return in my 125. the return is a seperate set-up than the return line.

40x is really meant for the current rate for a display tank with high flow corals.

here i thought we were talking about for through a sump or a fuge.

lets also keep in mind there are two different types of flows
there is current, this is the total current in the tank including closed loops, HOB filters powerheads, etc... this should be over 10x, how far over depends on what your stocking

then there is turn over, this is the about of water that is entering/leaving your tank going to a sump, fuge, or both. this rate is determined by what you system is like. with a sump, its doesn't matter, with a fuge you want the flow in the fuge low, so you keep this total number low

[poppin_fresh]

ok... my .02

Flow in the tank good, flow in the sump/'fuge bad. If you are using your sump to include a 'fuge and a place to house a skimmer you will want a lower turn over. As someone who's run a sump fast and slow I can speak from experience. Not only did my skimmer perform bad, I had micro-bubble problems with a fast sump.

I personally would plumb an overflow, or both, directly to a good skimmer. As long as the skimmer is rated for the amount of flow, you will get the best filtration. From the skimmer output you can then run a refugium which will help remove those nutrients that a skimmer wont.