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More FAQs about Plumbing Closed-Loop Return Manifold Rationale/Use

Related Articles: Plumbing Return Manifolds, Plumbing Marine Systems, Refugiums

Related FAQs: Closed Loop Recirculation 1, Closed Loop Recirculation 2, Closed Loop Recirculation 3, & FAQs on: Designs, Plumbing, Pumps, Troubleshooting/Repair, &  Marine Plumbing 1, Marine Plumbing 2, Marine Plumbing 3Marine Plumbing 4, Marine Plumbing 5, Marine Plumbing 6, Plumbing 7, Plumbing 8, Plumbing 9, Plumbing 11, Plumbing 12, Plumbing 13, Plumbing 14, Plumbing 15 Plumbing 16, Plumbing 17, Plumbing 18, Make Up Water Systems, Pumps, Plumbing, Circulation, Sumps, RefugiumsMarine Circulation 2, Gear Selection for Circulation, Pump Problems Fish-Only Marine Set-ups, Fish-Only Marine Systems 2, FOWLR/Fish and Invertebrate Systems, Reef Systems, Coldwater Systems, Small Systems, Large SystemsWater Changes Surge Devices

Is this clear?

Closed Loop vs. Powerheads         12/19/15
I am building a new 220 gallon display system, but can't seem to find recent answers on whether closed loop is still a solid choice for circulation.
<See WWM re my and others archived opinions.... Is NOT IMO.... better by far to provide all circulation "in-tank".... less chance of leaks, disasters, easier to regulate volume, direction of flow. Less likelihood (because the previous are sub-divided by using more than one pump) to avoid problems/issues w/ intakes... Less money for operation as well>

My current tank plan looks like the attached image. The closed loop(s) would run from the two drains low on the back wall of the tank to the four return holes at the front of the tank and the two return holes low in the back of the tank. I am considering driving the closed loop with either one or two Vectra L1 DC controllable pumps from EcoTech.
<Good products>
Two L1 DC pumps on reef crest random mode should produce about 1800 GPH each on average with peaks at about 3000 GPH each. This I believe will be plenty of turbulent flow for my reef, while a single pump might be sub-par as well as less turbulent. The return pump will be supplying the to returns at the top of the tank but its flow will be much lower (and constant) so I am ignoring it for circulation purposes.
<I wouldn't.... the air/water interface is the best area for providing such>

The question is: based on what I've read here and elsewhere, it seems like many aquarists are favouring various modern powerheads rather than closed loops.
<Mmm; better labeled as internal or submersible pumps>
What is the consensus of opinion (if there is one) among the crew about the suitability of my design / the general suitability of closed loops for reefs in today's (2015) technology?
<Can't won't speak for others, but all our input is stored here:
and the linked files above. For me; they're an inferior idea, technology.
Bob Fenner>

A Fork In The Circulation Road/Closed Looped Systems/Wavemakers 2/2/10
<Hello Matt>
I have a question for you. I've read you're webpage for years and have learned much, however, I have searched and was unable to find an answer to a dilemma I am currently facing.
I see a significant detritus build up in my tank, and I have a friend that is a huge proponent of a closed loop system for circulation, and I must say that I am strongly considering it.
<Cerith and Nassarius snails are good choices for eating detritus.>
I currently have a non-drilled 5-foot 110 gallon Oceanic aquarium. I am using an overflow box to drain water to my sump for skimming, media and refugium, and two Koralia 4's and two Koralia 3's for circulation. My water
parameters are within normal ranges, with the exception of slightly elevated nitrates, which I suspect is due to the detritus build-up.
<Very likely. Do you vacuum the sand bed during water changes?>
My question is this: If you could do either, would you go with a (Tunze) WaveBox or a closed-loop circulation system? What would you consider the pros and cons of the two systems. I like the WaveBox because of its ease
of installation, but am willing to make the effort for the closed-loop if it is truly the better option. I would like this move to be a long-term solution, as I am growing weary of throwing Koralias into the tank.
<Geez, I would think 4100gph of water flow out of the Koralias would be plenty for this system.
But to answer your question, I'd go for the Tunze Wavebox if budget wasn't an issue.
You may want to read more detailed info from Tunze in the following link.
You may be able to use the Nano Wavebox which is rated for tanks up to 158 gallons.
Watch the video also, very interesting.
Thank you for your time.
<You're welcome. James (Salty Dog)

Re: Marine Set-Up/Return Circulation Concept ... reefgeek cont.    4/8/06 Aloha WWM Crew!!!!!, <Hello John, James here today.> "Reef Geek in training" here.  Great site by the way...lots of great ideas and pics!!!...thanks a lot.  <You're welcome.> I have always referred to your site for great info.  I have scoured your site looking for some answers to my circulation concept detailed below, unfortunately without success.  I have kept a FO tank for quite a few years and now am making the "jump" into a reef.  I'm taking my time and doing a lot of research (maybe too much)....<Can never be too much.> I learned that lesson from keeping my marine tank.  I was hoping you might be able to give me your opinion on a return system I've planned and diagramed out. I have a 75 gallon tank 48 x 18 x 20.  I know circulation needs to be a lot stronger than I'm accustomed to, along with a lot of other things. I am trying to ensure there are to be no "Dead Spots" with regards to circulation, especially behind the reef itself where it meets the glass.  <A good idea.> I have an "in wall" set up for my tank giving the "window effect" so the traditional rear reef wall reef won't work for me.  My aquascape is going to have 2 slopes on either side of the tank....meeting in the middle.  I'm just more concerned if this will work and be worth my time, effort and $$.  I know the trend is to do a separate closed loop system but I'm really trying to stay away from that concept.  I'm extremely limited on cabinet space and due to the "in wall" set up and plumbing it would be a nightmare if not impossible. My thinking is I'd really hate to see the return flow from my main return pump connected to my sump just "go to waste"........so to speak......by simply pumping it back into the display tank arbitrarily.  Why not take that flow and by directing to certain areas within the tank thereby putting it to good use. <Indeed!>  Anyways, here's my plan.  As of right now my plans are to use 2 MaxiJet MP900 "Tunzean Like" mod.s located on either side of the tank pointed at each other directing flow side to side, cycling on a Chauvet timer. I know...bad idea with the timer cuz it will shorten the life of the pumps, but I really like the "waving effect" it the timer will produce with the corals so its worth prematurely replacing the pumps at a cost of 30 bucks. <MaxiJets are one of the few that work well with wave making timers. Should last quite some time.>  From my return standpipe I would construct either out of pvc and/or loc-line a return system with "down tubes" placed behind each reef wall as well as nozzles directing return flow from front to back....directly opposite to the flow of the MaxiJets for a lot of turbulence.  Here's my diagram.  

Re: Marine Set-Up/Return Circulation Concept    4/9/06 James,  <John> Thanks for the reply!!....from what you've said...I think I'm gonna move forward with this.  I do have one more "curve ball" to throw your way.  I have been doing some research on the SCWD.  I'm sure you are familiar with this device...just in case........ www.2iqventures.com I'm tempted to install one of these at the top of my return stand pipe and route loc-line and/or PVC in 2 separate directions (equi-distant in length from the SCWD) still incorporating the "down tubes".  The SCWD would now allow me to direct nozzles both front to back and back to front in an oscillating flow pattern....I like that!!!! Do you see any issues with this?  <No, give it a try, is a nice unit.> Also, correct me if I'm wrong here....isn't one of the goals of a proper operating return system to have the flow rate of the overflow match the flow rate back into the tank as closely as possible?  <Ideally, the overflow should be capable of handling a little more flow than the pump can produce, eliminates fiddling with gate valves.> If this is correct, then my flow rate at the top of the stand pipe being approx 1150 gph even with the SCWD and all the T and L fittings in line should still be pretty strong...thinking around 1000 gph. I'm not really sure of the flow rate of my overflow (1 inch PVC stand pipe).  I think its approx 850 - 900 gph.  If this is true I will need to tweak my gate valve to have them match.......make sense?  <Yes.> Lastly, if this is a viable concept.....then why even bother with a closed loop system and it's extra costs?.. i.e.: extra pump and it's associated monthly electrical bill. <Closed loop offers a little more versatility and a cleaner look in the tank.  Some aquarists look for aesthetics, not wanting all this stuff in the view.  Myself, I prefer the wave making effect, believe the corals react better to this concept.  My galaxy coral loves it, very nice to watch the tentacles shift back and forth.> Thanks for the calculator...going there now to do some math. Again, thanks for all the help.  <You're welcome.  James (Salty Dog)> John

Closed loop... alternative to powerheads, heat production   11/8/06 Greetings from Canada... A couple of quick questions.... 1-a closed loop of 6' long x1' wide powered by an 1800g/hr Mag drive pump. How many outlets (minimum/maximum) can it handle to deliver adequate flow through 1/2" CPVC? It's a 125 gallon tank...72"x18"x24".. <Mmm... six to eight is about maximum/ideal here> The loop will be hung from the cross members in the centre of the tank as it's impossible for me to run it along the perimeter or build a sump. 2-The pump is going to be hung inside of the tank. Will it cause heat issues? <Will contribute to 1/2mVsquared here to an extent, yes> I currently run 8 powerheads <! Time to look into fewer, more powerful? Perhaps a "Tunze" Christmas this year?> so will there be much heat difference as I will obviously be removing the powerheads have appr 120 liverock 5" oolite aragonite sandbed and a remora pro skimmer. Thanks for your time and response...Pete <Only real time, experience can/will tell here... Mag pumps run hot... I suspect hotter than your collective powerhead assemblage currently. Bob Fenner>

Plumbing, marine, closed loop Hi Guys....wonderful site. Many thanks >>Thanks back!<< A quick question if I may?  I have a 75g display, 30 g sump/refugium. Plumbing is a 1" bulkhead (I.D.) drilled at the back in the tank with a flexible hose going into the sump with a Mag Drive 9.5 forcing the water back up over the rim of the tank into a single elbow/effluent. A lot of flow/velocity...too much laminar I'm afraid.  But So far....the balancing act is perfect. Water level in sump matches the pumps output pretty nicely as there is no need to use the ball valve to divert flow. (this seems to defy the 600 gph flow rate I read about with a 1" bulkhead) I have been reading Anthony's suggestion about making a return manifold to more evenly disperse the water throughout the tank. Probably will give that a go this weekend. >>Great. Such a manifold works out very nicely.<<   Also, I have 2 small Rio's in the tank for additional flow,(240 gph each)  along with a Euroreef CS-6 skimmer in the sump stirring things up even further. Will this be adequate flowage for my setup? I do not have any livestock in the tank yet...just 130 lbs of Fiji rock. After scouring your site...I've seen that 20x tank volume is pretty much the norm these days. I do want a few fish...but mainly corals and inverts. >>You don't really need 20x moving through the sump. More flow in the main tank is nice though. >>The Rio's make me a little nervous though, they have a rep for burning/shorting out<< I was wondering if adding a closed loop system would help? Or, is this overkill/un-necessary? >>If you want more flow, sure! Sadly, the amount of flow in a tank is partly a function of the corals you keep and personal preference. I know on my tank, I never seem to have enough flow regardless of all the extra closed loops I add!<< I do not want to drill additional holes for plumbing, so I was thinking about looping pvc from the top of the display tank, gravity feeding into another Mag-drive of some sort, (size recommendation would be helpful) then shoot right back up into the display (no even going into the sump...just independent) maybe splitting the effluent  into 2 feeds?  ("T") this way...could I eliminate the Rio's inside the tank? >>Sounds good to me. I like removing any kind of power head from the tank, and I run my closed loops over the top instead of drilling - I think it give greater flexibility for the future. You can also look into a device called a SCWD that is basically a 'T' that alternates the current between both sides of the 'T' by a series of gears powered by the water flow. There are, or course, more expensive options like the oceans motions 'Squirt' - I just got one to replace two SCWD's and I love it so far! As for pump size, that depends on how much flow you want. Mag 9.5's seem to be a good all around size. << Thanks so much for the insight... >>Hope it helps!<< Mike Gaydos >>Rich<<

Re: Plumbing, marine, closed loop Hi Rich, Thanks again for taking the time to respond to me. All this information is surely a lot to digest for a newbie like myself, but I keep reading and learning. Anyway, I guess my main misunderstanding about flow rates comes into play when the term "turnover" is used. I thought 20x tank volume meant all water must go thru the sump. So then what you are telling me is not all of that 20x must go thru the sump but rather just get "moved around" by a combination of sump, skimmer, powerheads in display, and closed loops?? >>That is exactly what I am telling you! Its important that there is 'enough' flow around the corals, not that all the water  must pass through the sump>> Could you please tell me what the desirable amount of water MUST move thru the sump/skimmer to be effective at filtration and the rest just for water movement? >>I can give you a sideways answer - as much as possible.         In my case, 600 gph moving thru overflow/ return, 350 gph thru skimmer, and possibly another 600 gph moving thru a closed loop over the top of the tank be adequate? Sure seems like a lot to me.... >>The skimmer doesn't count as flow or turnover unless it is a HOB skimmer. The animals in the tank could take more flow, but you don't have to add more unless they need it. Does it move around the tank briskly? Are there no dead spots? Then you are fine! >>      One other question please about closed loops. How do you prime the pump if it is fed by the line hung over the top of the tank? >>The easy way is to fill the line of the loop with water before you hang it over the top of the tank. You can also plumb in an ball valve above the tank so you can open it and fill the line with water. That makes sense, really>> I'm sure the supply must at least originate roughly in the middle of the tank with some sort of filter/screen over it as not to suck in anything undesirable? >>Screen yes. You can put the intake where ever you like in the tank (I hide mine behind the rockwork) or if your overflow will take the extra flow, you can stick it in the overflow.>> Once it is primed...it should continue on until power is disrupted or would it continue to siphon? >>Yep! (ok...that was 2 questions) >>3!>> Oh....one more....please......where does one drill the anti-siphon hole in the manifold as described by Anthony?  Cant have it above the water or it will spray while running....so in the "loop" somewhere pointed downward or is it even necessary at all? >>Some people don't use them, but they are a good idea. If the power goes out, the manifold will continue to siphon your tank. The anti siphon hole does go slightly above the water line, drilled in such a way as to point slightly downwards so its 'spray' doesn't hurt anything.>> Thanks so much....really! Sincerely Mike Gaydos  (rookie) >>My pleasure!>>
Re: closed loop
Can I take squeeze in another closed loop question? I'm pretty clear on flow rate now...thanks to you. Could a person who only has the lone 1" overflow bulkhead installed (with limited 600 gph capacity) plumb in a closed loop hung over the top of the tank.....gravity fed into a pump, but them have the effluent merge into the manifold to increase volume that way? The manifold will be 3/4 with at least 6 elbows/returns. Should have plenty on room in there for the extra flow provided by the closed loop?!? This make sense? >>Makes sense but is generally considered a bad idea because it makes the pumps 'compete', or push against each other>> One last thing.....Will the Kansas City Chiefs be able to make the playoffs with the rather rocky 1-3 start this season? >>Sadly, no>> And if you could supply me with the winning Powerball lottery numbers that would be cool too... Thanks a bunch. >>7 3 8 9 5 33>> Mike >>My pleasure>> >>Rich>>

Water flow options: manifolds 3/16/05 Dear Anthony <Cheers, mate> I read with interest your article on flow in a reef tank. I, like most aquarists with an advanced set-up have more than my fair share of Maxi jet powerheads in the tank. I have however got a very large Eheim 1080 with a return overflow box servicing most of the flow within the tank so flow is quite turbulent (on the return side of the tank). I do however have dead spots which I have removed (not very successfully) with the use of an array of powerheads. <Indeed... that's a challenging way to go about it> Do you know of a method of attaching LocLine modular hose to one of these buggers? If not then a pump that I can purchase here in the UK that I can sit in the sump and array with LocLine manifold and pipes? Would benefit from your suggestions here. <I do believe the closed loop manifold with a single pump or two is best for the long term. Do read the thread of links stickied at the top of the All Things Salty forum at reefcentral.com. A couple dozen fab threads with pics> PS Good article on flow by the way (anemone owners take heed). Regards Jim <Thanks kindly my friend :) Anthony> 

Closed Loop water circulation 3/16/05 I've been not able to see answer to a basic question about closed loop schedule. <do see the extensive list of links I have to this subject over in the "All Things Salty" forum at reefcentral.com. There is a sticky thread at the top of that forum... many posts with pics :)> My setup is a 180g reef + 75g sump. I setup a closed loop with two 1" intakes in the two overflow boxes to feed a Dolphin Ampmaster 3000. The return is made in 9 different locations in the tank. The tank has been running for 3 months and my soft corals and fish are doing fine so far. <ahh, good to hear> I run the closed loop continuously - no stop. Do you think it is a good idea or do I have to produce some kind of intermittence? thanks, Didier <random turbulence is very fine and arguably better. Leave it exactly as you have it. Wave timers are not needed. A waste of money IMO, although current switching devices (versus wave timers that shut off pumps intermittently) are novel. Anthony>

Water Return Manifold 7/19/05 Dear WWM Crew,     I just read over Anthony's article on water return manifolds and had a few questions regarding it.  First, I gathered that it is usually used for larger systems but was wondering if it can also be used with smaller aquariums (ex. my 30g reef) <Yes>   I'm sure it could be adapted to my aquarium but for a 30 gallon reef that will be holding some medium current LPS corals how many tee outlets should I use?   <Four, six...> And finally should I add any special nozzles to the tees for better flow? <Could... I like the "Loc" types for ease of directing... there are threaded (male) bases available... to fit PVC female...> That's all I need to know for now. Oh, and before I forget, please give my regards to Anthony for a very well written and informing article. Thanks, Andrew <Will do. Bob Fenner>

Internal Horizontal Overflow? 9/24/04 I have been reading the FAQ's on the internal horizontal overflow design by Anthony <its not much of an original idea, per se... but popularized with my "book of Coral Propagation" FWIW... I've used it for many years as have others. Its tidy and quiet... can be easily hidden too (encrusting inverts on an extended floor to the box> and would like to try this idea out on my new acrylic tank (approx. 140 gal).  My tank measures 48" wide X 24" high X 28" deep.  I have not had the overflow built or drilled yet as I want to make absolutely sure that they are located in the right place before I have them built/drilled.  I was initially going to just build the standard internal overflow, but this new idea of the horizontal overflow has me intrigued.   <yes... and besides sparing that dreadful and noisy floor-drilled tower... a horizontal box stretches thin surface overflow water for improved skimmer performance> I was planning on keeping some hardy soft corals and some reef safe fish, nothing extravagant yet.  I was planning on doing all live rock filtration with a AquaC EV-180 protein skimmer, <excellent> small 15 gal refugium with macro algae (I don't have a lot of room in my stand), and a 6" deep sand bed (both in the refugium and main display).   <all good> For lighting, I was going to either go all VHO's or metal halides with PC's.   <pick your corals (a specific list by species) before you pick your lights... only then will you know what to opt for based on their actual needs> By the way, for a hood design how far should the lights be from the top of the acrylic tank and should I cover the two holes in the top acrylic plate/brace that give access for feeding, etc.   <fluorescents should be no more than 3" off the surface... but halides need to be minimum 6-9"... higher if higher wattage MH lamps> My question is actually about the overflow and the manifold.  I believe I read that about 2" from the top and sides for the holes (equally spaced) for the drain, and same for the return on the opposite end of the tank. Now, I have a Pan World 50PX-X (comparable to the Iwaki 30 RLXT) and want to maximize flow.  What would you suggest based upon my setup would be the best design of the horizontal overflow as far as spacing, hole size and number of holes for the drain and return, <as long as you can comfortably and practically make it... the longer bos spreads surface over flow water thinner/better> and what would be the best design for the manifold. <little to worry about here... work around any structures needed... but essentially form a closed loop circuit fed by one supply tee for improved distribution of flow> Also, if the holes are about 2" from the top of the tank, is this going to adequately "skim" the surface of the water to provide maximum efficiency for the skimmer?    <depends... if the nutrient load is high... this will work fine. But for hardcore reefs with good nutrient export, you will notice the benefit of the horizontal overflow more so here> Just though I'd ask plenty of questions before I have my tank drilled past the point of no return. Also, are the bulkheads just open on the inside of tank since there isn't a "pre-filter box" or do I need to in close the holes with some sort of "box"?   <just strainers on the interior bulkheads> I love your site and am glad you guys are here to help educate us. Mahalo, Chris <thanks kindly... best of luck/Life to you. Anthony>

Closed loop manifold 9/24/04 Hi Anthony. Can I build manifold as main return, or do I need to run it separately? Thank you <either way is fine my friend... some folks power it by their return pump... others use a submersible pump inside the tank to power it regardless of a sump pump or not :) kindly, Anthony>

Powerheads v. Closed Loop This is in reference to 180 gallon reef tank with sump in the basement. Possibilities for moving water include: 1.) Two pumps in the basement returning water to the tank and running in series (or parallel?) 2.) One pump in the basement returning water from the sump to the tank, and 4 powerheads in the tank (maybe with a wavemaker) 3.) One pump in the basement returning water from the sump to the tank, and a closed loop (circulation only) with the pump sitting upstairs underneath the tank. I don't see the advantage to option #1, i.e., having two pumps downstairs pulling water from the sump and running in series. By "in series" (or parallel?), I understand this to mean that if one pump goes out the other one would still carry the job (pulling water through the sump and the skimmer), albeit at reduced capacity. But why do it in series? <I prefer separate runs.> If you're that concerned about the pump failing, it would probably be more efficient and cheaper in the long run just to have a spare pump. <I am an aquarium maintenance professional that works out of his home, so I see things from that perspective. While for you and your own tank, you maybe perfectly happy with a spare pump sitting unused in the house. I don't want any more stuff than I already have to have around and I doubt any of my customers would want one either. I try to consider every possible catastrophe and design systems so that no matter what goes wrong they will continue to function and not flood. It is a liability issue for me. Also, if a pump were to fail, with two pumps, I can get to replacing the broken one when I have time. If there is only one main pump, I would have to drop every to fix it immediately.> Option #3 seems better than #2. <Much better!> I perceive the advantages to using a closed loop as follow: Aesthetics (no unsightly equipment in tank). And less heat in the tank. In favor of using powerhead, I saw the following idea to conceal equipment in the tank: do not make the rear center overflow flush with the back of the tank, rather set it forward 6" or so and hide the equipment behind the overflow. This also has the benefit of flow coming into the overflow from all four sides. Your thoughts on the above issue would be most appreciated. Aryeh L. Benjamin <While closed loop circulation is very popular, I routinely hear of individuals with a mobile invertebrate (anemones and snails are the most common) being turned into chowder enough that I won't use one. I prefer to get my 10-20 times turnover through overflows and return pumps. -Steven Pro>

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