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Why is there a common trend to grossly oversize return pumps on a new build.

Water Dog

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Here’s a prime example of a popular 1400 gph DC controllable pump only actually pumping 250 gph at full throttle as measured by a flow meter. Head pressure loss due to height, plumbing restrictions and elbows do a lot to reduce flow, more than many are actually accounting for IMO.

 
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gray808

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Turning over your tank so many times will just strip your reef of nutrients needed to grow.
Question 2 is did you know that high turnover in a sump could be stripping beneficial nutrients from your corals and impeding growth even if you are satisfied with how your tank is operating?
Where? It depends totally on your setup but if your running filter media, and socks, your stripping your tank of nutrients prior to being used by corals. Ask WWC who runs around 2-3x return system.
How does it strip nutrients?

Say I have some nutrients, we'll call it N, and my flow is F(x).
Why would the drop in N happen more with a high x flow?

If this is true, and you are looking for high N, it would imply that you should have the lowest x possible.

What process within the flow is taking away nutrients?
Where do they go?

--Gray
 

ErehwoN

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So if you take out the upgrade aspect and someone purchased a Red Sea 525xl (139g) Deluxe that fit their home appropriately, and asked you to recommend a return pump would you recommend they get a 5000gph return pump? or a more conservative 2000gph pump? Considering the life expectancy of the pump and likely hood that they will upgrade the tank in less than 10 years.

The real question I asked this was to indirectly understand myself as well as see how other people evaluated return pump flow. Rather than just looking a build over build and following John Smith because he has a sweet build so his return pump size must be necessary. It seems its common for people to feel that more flow through their sump = better. However, I have had discussions with some pretty well regarded folks in the industry that this just isn't always true (obviously largely dependent on setup).
To answer the first question, I have to say I would recommend the more conservative pump because the setup described is much less DIY than what I've cobbled together in the last 4 months. When I started this whole project I was even more naive than I am today so it was a piecemeal design rather than saying, "Oh, THAT is what I really want" before I got started. That's why I've named my little biosphere "Tankenstein".

I do appreciate your viewpoint of people "keeping up with the Joneses" or just buying the shiniest thing they can rather than doing the math and getting the best pump they can for the money that's appropriately sized. For me, I really do hope to upgrade in the next year, but with the volatility that 2020 has produced, I'm happy I've gotten as far as I have.

Jim
 
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Palegic

Palegic

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How does it strip nutrients?

Say I have some nutrients, we'll call it N, and my flow is F(x).
Why would the drop in N happen more with a high x flow?

If this is true, and you are looking for high N, it would imply that you should have the lowest x possible.

What process within the flow is taking away nutrients?
Where do they go?

--Gray
Are you being facetious or asking for real? Most people run socks which would immediately strip most nutrients passing through. Additionally even if not running a sock, biologic or chemical filtration via means of scrubbers, reactors, or fuges will strip nutrients. The more times per hour you turn over your tank the faster these nutrients are depleated within reason. Sometimes it's beneficial to use the natural consumption and filtration via means of fish, coral, and inverts in the DT vs sending everything through the sump.
 

gray808

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I am being serious. You didn't state a thing about OTHER THINGS, especially other things placed there with the intent to remove nutrients, being the cause of removal, just too high of flow.

Looking at it that way, I can see one argument for higher flow: if you have, say bio balls or other media in the sump, a higher flow seems like it would give the nitrifying bacteria more of a shot to convert/denitrify, than they would have with a more slow flow.

But I'm new, so my opinion isn't really formed yet.

--Gray
 

Mastiffsrule

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I have never really looked at pumps ratings more than what the claimed “range” is . I think their manufacturer posted max per gallon could never be reproduced in an actual tank setting. Just an opinion, no facts to back it up. If the pumps mid range matches what I need that is what I go for. In some years of keeping tanks I have never once measured flow by more than watching and adjusting. unless I am hooking up uv.

Now if you want flow, step up to the big boys. Go Abyzz pumps and water cannons. They are rated or a 20 long to 1200 gallon. :eek: o_O :D

1597360997712.jpeg

1597361068275.png
 
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Palegic

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I am being serious. You didn't state a thing about OTHER THINGS, especially other things placed there with the intent to remove nutrients, being the cause of removal, just too high of flow.

Looking at it that way, I can see one argument for higher flow: if you have, say bio balls or other media in the sump, a higher flow seems like it would give the nitrifying bacteria more of a shot to convert/denitrify, than they would have with a more slow flow.

But I'm new, so my opinion isn't really formed yet.

--Gray
To elaborate there are two types of flow. In tank turnover which has no effect on stripping nutrients then there is return flow or flow through the sump. It's important to understand the difference.

Also, I'm not arguing at all or really even debating. I'm just questioning something I have been seeing lately to better educate myself and possibly others.

You hit at some point the law of deminishing returns with return flow. Where it's outpacing what your sump can process. By using mechanical filter media your scrubbing the system of the remaining nutrients before allowing the system to process it. Yeah maybe you have super low nutrients, and a ultra clear tank, but there are organisms in the tank that might be able to naturally use these to grow. There's a balance and from what I have heard 2-5x is more than enough and really no reason to shoot for higher return pump turnover.
 

tbaity1401

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I think it really boils down to the following:
1. Reduced GPH given plumbing as others have pointed out. Obviously case by case but its probably 50%+ reduction for most
2. Running a pump lower than max output probably increases longetivity and is quieter.
3. Biggest reason is probably perceived value of larger pump. Most larger pumps are only +/- 15% more expensive than the smaller version. Once you've made the decision to invest in a certain brand, you're most likely to pick the larger version because the investment in the larger pump isn't as big as the initial investment. Good marketing! ;)
 

Tjakes680

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I have always gone by 10x rule since I started reefing witch has been since the 90 s and I ran all my stores and customers tanks the same way with success I would say 25x50x is a little much but I see no problem with 10 but then again im a old school reefer
 
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Flippers4pups

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@Palegic,

"Question 2 is did you know that high turnover in a sump could be stripping beneficial nutrients from your corals and impeding growth even if you are satisfied with how your tank is operating?"

In all due respect to you, it would be the opposite. Slower (less flow) dwell time with your skimmer would remove more nutrients, not higher flow. Higher flow through the sump would allow more solids to be captured by your filter sock, but have a small impact on N03 and P04.

Maybe I need you to go in to detail more from your point of view to understand your statement? Respectfully.



"Well you loose redundancy by running equipment off a manifold from the return pump and it makes it more difficult to measure the flow through your sump."

Sorry, again not sure what your mean by "redundancy" here. If you have a return pump go out and your running a separate pump for your manifold, the manifold pump would be just recirculating the sump water until your return pump came back online. I don't see any redundancy here.

Flow through the sump would be the same with or without a separate pump for the manifold. Flow is measured by the amount draining into the sump from the DT, regardless, not the other way around. Respectfully.
 

bct15

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Nutrients are not pulled out instantly in fives and scrubbers. Nutrients being pulled out through most biological filtration will depend on dwell (contact) time. If the water is moving through the filter faster, the contact time is much lower and you will pull out less nutrients.
 

bct15

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Secondly if you are turning over less water through your sump than your protein skimmer has passing through it, then your protein skimmer is just skimming already skimmed water...which diminishes its efficiency.
 
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Palegic

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Nutrients are not pulled out instantly in fives and scrubbers. Nutrients being pulled out through most biological filtration will depend on dwell (contact) time. If the water is moving through the filter faster, the contact time is much lower and you will pull out less nutrients.
What about filter socks?
 
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sawdonkey

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Question 2 is did you know that high turnover in a sump could be stripping beneficial nutrients from your corals and impeding growth even if you are satisfied with how your tank is operating?
I don’t think most people run socks. Many do, but I don’t know about most. I don’t.

I’m with flipper above about dwell time. Your skimmer can only do so much foaming and feeding it more dirty water won’t make it more effective.

But even if your assertion is true that more turnover strips nutrients, who’s to say that’s a bad thing. If it is true.......I’m off to go buy a bigger return pump! For many, keeping nutrients down is a bigger challenge than keeping them up.
 

Rob.bucek

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Here is a fairly popular DC pump on the market. Look at the chart, take height of the stand, add height of the tank and then few feet of loss due to elbows and you end up with about 8ft of height which would give you about 1300 GPH (50% plus loss).

Change its ouput down from 1.25" piping to 1" and/or add a manifold and you'll be lucky to get 800 GPH.

Quite a bit more than 20% loss

With these numbers a 125-180 Gallon tank would have 5-6x flow - not more.

1597348944951.png
That right there is why I'm going with two COR-20's on my 180. They don't handle head pressure well, I also get some redundancy without having to run them wide open. I will not have a manifold in the mix.
 

Bleigh

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So if you take out the upgrade aspect and someone purchased a Red Sea 525xl (139g) Deluxe that fit their home appropriately, and asked you to recommend a return pump would you recommend they get a 5000gph return pump? or a more conservative 2000gph pump? Considering the life expectancy of the pump and likely hood that they will upgrade the tank in less than 10 years.

The real question I asked this was to indirectly understand myself as well as see how other people evaluated return pump flow. Rather than just looking a build over build and following John Smith because he has a sweet build so his return pump size must be necessary. It seems its common for people to feel that more flow through their sump = better. However, I have had discussions with some pretty well regarded folks in the industry that this just isn't always true (obviously largely dependent on setup).

I over purchased planning to upgrade as well. I would not have purchased such a large pump if that wasn't my intention. I would also not recommend someone over purchase as much as I did if they don't even plan on using that pump in a bigger tank. I think I would still stay within the 10X range for a few reasons. 1) You will never get the amount of flow the manufacturer claims; 2) I do not want to run the pump at the top end of it's capabilities; 3) The flow will be impeded more the longer it runs due to gunk build up in the pump and the pipes.

I am fully on board with the 2X-3X turnover and that's what I attempt myself, which means my pump runs really slow. My pump is likely rated at 20X-25X turnover for my tank, but I have almost always ran it around 2-3 out of 5. I also don't think it has ever been at the max turnover that the manufacturer says it could do, even when running on the highest power. I also have a manifold hooked up, so some of the turnover is going to other things, even with me running it as slow as I do.
 

pdxmonkeyboy

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Sigh... Filter media does not absorb or rob the tank of nutrients. In a high flow sump you are actually passing more water over filtered detritous in your sock or matt.

Same goes for a skimmer. The skimmer processes X gph. Period, regardless of the flow through the sump. It could be said that higher sump flows pull LESS organics out of the tank as the skimmer is only processing a percentage of flow.

The amount of flow through the sump has little to do with organic content in the tank. If you have rocks in your sump there are plenty of areas of low flow... the boundary layer of water next to the rock.. the only part that microbes have a chance to process is barely moving. Much like the water in a raging river, the bottom 1/32" of the water column is barely moving.

But again.. besides rotting food, ammonia is secreted by a fishes gills and is not affected by filtration.

FWIW..i am running a reeflo hammerhead with around 3,500 Gph to the DT. But i also have low flow areas in my fuges.
 

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