Linear Inches Of Overflow??? And Sump Turnover

[JaySchulz]

Ordering my tank this upcoming week and trying to make the last few calculated decisions. I want to hear any opinions or suggestions before I spend $4k on tank plus stand/canopy.

My biggest dilemma is that I will be doing a peninsula style tank. (72" x 36" x 21") and I want to keep powerheads off 3 viewable sides if possible. This means I need about 8" on both sides of the overflow to put mp60's (4" width of mp60 plus 2" of glass between edge of tank and powerhead + 2" of glass between powerhead and overflow) or what ever powerheads I decide on. I was planning on an mp60 on each side of the overflow. That equals 16" of glass that cannot be covered by an overflow. Now I'm left with 20" of glass due to 36" wide tank.

Let's back up a little bit now. I used the RC calculator for overflow size and was met with the question of how many GPH of turnover through the sump. I decided that 4x turnover through sump would let the protein skimmer work effectively (DO YOU AGREE).
So with 236 gallon tank with roughly 75 gallon sump/fuge= 300 gallons (roughly) which would mean 1200GPH with 4x turnover.

At 1200 GPH the calculator suggested 18" of overflow. I've calculated that with teeth on the overflow and the overflow extending into the tank 6" I will only have 16" of overflow. Will these missing 2" really make a huge difference on the efficiency of the system as a whole. Plus if we all felt that 4x turnover through the sump was not enough, I would seriously be lacking the amount of linear inches required to effectively skim the surface of the water.

Let's hear what everyone thinks. Thanks a lot ahead of time.

Ps if this was confusing I can draw up some diagrams

 

[Breadman03]

Linear Inches Of Overflow??? And Sump Turnover

The overflow doesn't need to go to the bottom of your tank. It just needs a few inches from the surface of the water, so your MP's will have plenty of room.

Do some searches on the "BeanAnimal overflow." I'd find some links, but that's a bear on my phone.

Put this in Google: "BeanAnimal overflow site:reefcentral.com"

 

[CuzzA]

Yep. Put the powerheads below the box. The internal box will only need to be about 5 inches below the waterline. I would not have teeth on the weir as it will cut the surface skimming in half. Instead attach plastic gutter guard behind the weir. I would also consider having your return outputs up and over to the opposite side of the overflow so the the large surface area of water is pushed to the small overflow. A couple sea swirls might be a good idea.

 

[dave.m]

An external overflow would leave all sorts of space for powerheads.

Another option for water movement is using returns from your sump that enter from the top of the tank. These can be run down the full length of the tank within the canopy so that you get water movement from the far end without visible pumps. The alternative, of course, is a closed loop that comes up via holes drilled in the bottom of the tank.

I disagree about overflows not having teeth. While a straight overflow will draw off surface oils most efficiently they are a failure at drawing suspended detritus. The teeth in the weir have been used for decades in aquariums specifically because they break the water's surface tension, adding the turbulence required to break up surface oils as well as draw suspended detritus.

Dave.M

 

[CuzzA]

I disagree about overflows not having teeth. While a straight overflow will draw off surface oils most efficiently they are a failure at drawing suspended detritus. The teeth in the weir have been used for decades in aquariums specifically because they break the water's surface tension, adding the turbulence required to break up surface oils as well as draw suspended detritus.

Dave.M

Sorry, but I have to totally disagree with you. The ONLY purpose and REASON why teeth were ever created for the weir was to keep inhabitants out of the overflow box. The very mechanics of a weir breaks the surface and removes the bouyant surface debris common in reef tanks. Teeth do not provide any extra surface skimming capability. Taking water over the weir from the water column is actually worse than taking the thin sheet of water from the surface. This is what happens with teeth because the water level is raised due to the resistance the teeth are putting on flow. Basically, to get technical we want to filter the dirtiest water (skimmers perform much better the dirtier the water is) which is on the top layer rather than allowing the overflow to take water from below which is much cleaner and allowing the diry water to just sit on top slowly passing over the weir.

A simple DIY experiment would be to take a bucket and drill a hole one inch below the lip and add some bouyant debris. Then put a hose in the bucket. I guarantee you the bouyant debris will remain on the surface. Now take another bucket and cut a notch. The debris will pass right over the makeshift weir/notch.

 

[dave.m]

This has all been rehashed on several threads and is reviewed in The Reef Aquarium by Delbeek and Sprung. I will not go through it again and again. I simply disagree with you and democratically offer an opposing view.

Dave.M

 

[JaySchulz]

Thanks for all the responses.

My original plan was to do a bottom drilled triple durso style drain. Because of the size of the room the tank is placed in I really want it to be flush against the wall. I know this sounds ridiculous but the extra couple inches the tank would have to come off the wall if I did a side drilled drain would really start to block the walk path. Plus I like the idea of my bulkheads being under the stand and untouchable by my kids (I'm putting locking mechanisms on my stand doors).

I originally didn't want to do a peninsula style tank but it was the wife's request and getting approval to spend $8k+ on a new system was tough as it is. So compromising to make her happy seemed like the smart thing to do.

I haven't completely tossed around the idea of doing an internal beananimal or herbie style drain and I'm not opposed to it but even so, I still have the dilemma of the linear inches of overflow. Cuzza I was considering going toothless and that seems as if it would solve my problems plus I would have much more linear inches of overflow than necessary. I even considered going coast to coast without side drains but that eliminates the mp60's unless I give in to putting them on the opposite viewable glass.

 

[dave.m]

Or you could make the box of the overflow wide enough to accommodate both the drainage pipes (whichever style of drain you choose) plus the mounts for the powerheads. Then you could go coast-to-coast if you wanted to.

Dave.M

 

[sfsuphysics]

I have a 72" x 60" peninsula style tank, and I will say from experience, it is quite difficult to get sufficient flow with only powers heads on the back wall. I think I had at one point 15000 gph worth of pumps, and while it does move water, it's super easy to have dead spots. Was tempted to try one of those gyre pumps, but the acrylic is a hair over an inch thick and I really couldn't see how that pump would radically change the water flow. So I put pumps in each corner instead, and along the overflows.

 

[JaySchulz]

I have a 72" x 60" peninsula style tank, and I will say from experience, it is quite difficult to get sufficient flow with only powers heads on the back wall. I think I had at one point 15000 gph worth of pumps, and while it does move water, it's super easy to have dead spots. Was tempted to try one of those gyre pumps, but the acrylic is a hair over an inch thick and I really couldn't see how that pump would radically change the water flow. So I put pumps in each corner instead, and along the overflows.

I think that I have decided to give up on the thought of keeping powerheads off the three viewable panels. I was considering the gyre but was hoping to wait till the 170 came out.

 

[JaySchulz]

I think I've decided to go with a toothless overflow. Then if I ever decide to run a higher turnover down the line, I will be able too while effiently skimming the surface

 

[CuzzA]

Jay it's hard to tell until you have the tank aquascaped. I wouldn't take any ideas of the drawing board. Personally I think a could Vortechs or Jebaos under the box with your returns going over the top on the opposite side, perhaps with 1-2 Sea Swirls will provide you with excellent flow throughout the tank.

 

[rmgaspar]

Hello,

Instead of a toothless overflow why don't you do it like me?

You can have two tears across all the glass (one for overflow and the other for emergency) and then a small 15/20cm high on the outside of the aquarium.

More than enough space to place the Vortechs and I can assure you there is no live going to the overflow box. I can tell you that my astreas really try. The tears is 1cm

This is a picture of mine.

All the best,
Rui