I have done a lot of reading about these & still have one more question that everyone gives me different anwers to.
I have a 125 gallon reef tank, not drilled.
So I went with the double overflow & it works well & no noise.
Anyway, it goes onto my sump, protein skimmer & back up to the tank. I think it will have better filtration, since my tank is 6ft long?

What I am wondering is, has anyone ever hung two of them on the back of there tank. I want to set up a refugium on the other end, using an overflow, but have been told several times that I won't be able to balance out the water, either my sump will overfill, or the refugium will.
Don't really want a flood --- LOL.

Thanks everyone for any replies.

Put the refugium in series and before the sump. With an overflow from the refugium to the sump. that way the refug can be almost full to provide max water for the macros and pods. And the sump can still vary in water level for adjusting. Flow is from tan overflow-> refug -> sump -> pump ->back to tank.

Another option is to split your current drain with part going to the new refugium and the other going directly to the sump. Again the refugium drains to the sump also. But with this system you can adjust the flow in the refugium.

Both use the same overflow, pump, and return plumbing. to keep things all balanced out.

my .02

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fw leiden since 1979, fo salt since 1979, mixed reef 55g 2002-2009. Strong emphasis on the tank taking care of itself. Balanced with plant life, no water changes, tap water, no filters in FW. Only dosing calcium, alk, mag in marine reef tanks. http://www.aquariumforum.com/f15/my-...ods-26410.html
recent tanks (till 2009) 7 years- 10g FW leiden 7 yrs, 55g mixed reef 7, 2 yrs, 20g FW leiden, 10 g fw leiden , 29g mixed reef, current tank 55g leiden

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Given your current situation I think this is the best route to go by far. With a refugium that will have Macro algae in it for nutrient removal/uptake pushing water through it at a slow pace will net you better results as the water will have enough dwell time in the refugium for the Macro Algae to "clean" the water before it goes back into the system. This is in no way ment to be taken as there will be no nutrient removal, its just the slower the water flows the more time the Algae has to do its thing and the more effective it will be potentially. One of the biggest mistakes I have seen made on an other wise awesome system is the fact that a refugium had been set up in a sump that has 500 plus gallons moving through it a hour.

One of the post above made a good point about the flow going through the fuge. Doing two over flows(if you can get them balanced) would do one of two things eather have water rushing through it anyway not letting the Macro algae do it's job or if you use a ball valve to slow the water, fuge would still fill to fast and there's your flood.

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If It Is To Be It's Up To Me!!!
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Hi trouble.

Actually you would not have to balance out the two overflows at least in the sense that each would have to exactly 1/2 the total overflow.

What is important is a single sump. So that a given quantity of water is being returned to the tank at any one time. that way each overflow could be whatever. Like 1/4,3/4: 1/8,7/8 etc.

But if you have two seperate sumps than one could run dry, one could flood, while the other did it's thing. Or one could flood and the other run dry and so on.

At least that is the way I think it would work.

my .02

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fw leiden since 1979, fo salt since 1979, mixed reef 55g 2002-2009. Strong emphasis on the tank taking care of itself. Balanced with plant life, no water changes, tap water, no filters in FW. Only dosing calcium, alk, mag in marine reef tanks. http://www.aquariumforum.com/f15/my-...ods-26410.html
recent tanks (till 2009) 7 years- 10g FW leiden 7 yrs, 55g mixed reef 7, 2 yrs, 20g FW leiden, 10 g fw leiden , 29g mixed reef, current tank 55g leiden

How are you my friend it's been awhile? I believe that balancing two over flows would be next to impossible. I do how ever agree with you in that if you use one over flow feeding a fuge and that fuge feed the sump or vice versa would be more conceivable. The poster has one advantage he is using a dual over flow with two seperate outputs which would make it easy to feed the two units without adding another over flow. Only problem remains slowing the flow in the fuge unit(to enable the macro algae to be most effective) and keeping enough water in the return pump section.

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If It Is To Be It's Up To Me!!!
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Yes it has been awhile.

Little nit here the sump by definition is the lowest point in the system.

If the refugium was the lowest then the "sump" would then just be a skimmer /filter/whatever container. The refugium would then be a combined refugium/sump.

So hopefully the refugium is higher then the sump. and then refuge to sump is the flow pattern.

The important thing as I stated before is one sump.

With two overflows both capable for draining what is being pumped to the tank, one overflow could fail entirely with 0 water flow. (snail, siphon failure, plugged by algae etc etc etc) and the other overflow would still drain the water back to (eventually) the sump. And the system would continue.

In fact some even use two overflows to a single drain for that reduncy.

my .02

__________________
fw leiden since 1979, fo salt since 1979, mixed reef 55g 2002-2009. Strong emphasis on the tank taking care of itself. Balanced with plant life, no water changes, tap water, no filters in FW. Only dosing calcium, alk, mag in marine reef tanks. http://www.aquariumforum.com/f15/my-...ods-26410.html
recent tanks (till 2009) 7 years- 10g FW leiden 7 yrs, 55g mixed reef 7, 2 yrs, 20g FW leiden, 10 g fw leiden , 29g mixed reef, current tank 55g leiden

Just spit balling here but what do you think of this, and this is something the OP ran pass me and it sounds doable and I want to hear your input. using a mini-jet 404 & a 606 lay the 404 just under the water line into the fuge turned down to it's lowest setting pulling water out of the tank down to the macro at a slow pace and sent back by the 606. I do believe the fuge will be 20gal. Thanks

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If It Is To Be It's Up To Me!!!
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I am having trouble understanding or pictureing in my mind what you have in mind here. Perhaps a simple diagram would help.

If you are using two pumps in any way to pump water from the display and then back, then IMHO it will not work.

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fw leiden since 1979, fo salt since 1979, mixed reef 55g 2002-2009. Strong emphasis on the tank taking care of itself. Balanced with plant life, no water changes, tap water, no filters in FW. Only dosing calcium, alk, mag in marine reef tanks. http://www.aquariumforum.com/f15/my-...ods-26410.html
recent tanks (till 2009) 7 years- 10g FW leiden 7 yrs, 55g mixed reef 7, 2 yrs, 20g FW leiden, 10 g fw leiden , 29g mixed reef, current tank 55g leiden

I will post a diagram later I don't have the time rightnow I'm on my way out. And then we can go over it. Thanks.

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If It Is To Be It's Up To Me!!!
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After talking to several people & a couple of LFS, you are right, it won't work this way.
Guess the best & easiest is to go from the Ref, to the sump & then back up to the display tank, the only problem I have with that is, why mix the "clean water of the Ref" with the not so clean water of the sump?

My suggestion would be to get a larger sump and build the fuge section into it. This way you wouldn't have to worry about balancing at all. You could have as many overflows as you want as long as they are emptying into the same sump.

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Doc

Dr Hank's 200 gallon Reef Tank
http://www.aquariumforum.com/f46/drhanks-tank-3440.html

This is how I placed my refugium:



I have dual overflows in my display, and more than one return pump, my returns are drilled as well, and a lot of other stuff going on down in the stand (and next to the stand even!), so its not 100% accurate of the way I set my system up, but its the general concept.

I think that would work. Most would split the overflow instead of the ruturn line, but it should work. A lot would depend on how you have the specific system setup and the existing plumbing.

FWIW I ran a test with a refugium in series with the sump. I at first used 1 1/4" pvc pipe from the refug to sump. That was not big enough and the refugium overflow could not keep up. So I then tried 2" pvc pipe from the refug to sump and it could keep up. Just something to consider and by splitting the overflows or using your design, the problem could have been avoided by using valves to limit the flow to the refugium.


My .02

__________________
fw leiden since 1979, fo salt since 1979, mixed reef 55g 2002-2009. Strong emphasis on the tank taking care of itself. Balanced with plant life, no water changes, tap water, no filters in FW. Only dosing calcium, alk, mag in marine reef tanks. http://www.aquariumforum.com/f15/my-...ods-26410.html
recent tanks (till 2009) 7 years- 10g FW leiden 7 yrs, 55g mixed reef 7, 2 yrs, 20g FW leiden, 10 g fw leiden , 29g mixed reef, current tank 55g leiden