Please visit our Sponsors
FAQs on the Rationale/Use of Circulation & Marine Systems

Related Articles: Circulation, Inexpensive Wavemaker Impressions, by Steven Pro, Plumbing Marine Systems, Holes & Drilling, Plumbing Return Manifolds, Aeration, Water Flow, How Much is Enough, Powerhead Impressions by Steven Pro, Marine System ComponentsRefugiums, Central FiltrationFlow-through Live-holding Systems, Refugiums, Business Set-Up

Related FAQs: Marine Circulation 1, Marine Circulation 2, Marine Circulation 3, Marine Circulation 4, Marine Circulation 5, Marine Circulation 6, Marine Circulation 7, Marine Circulation 8, Marine Circulation 9, & FAQs on Circulation: Designs, Pumps, Plumbing, What's About the Right Amount, Troubleshooting/Repair, & AerationPumps, PlumbingMake Up Water Systems, Sumps RefugiumsGear Selection for Circulation, Pump ProblemsSurge Devices

Some Circulation Functions:

Aeration, aiding filtration, eliminating dead spots and excessive undesirable algal growth... making fun water movement for your livestock.

Flow And Filtration...Not Necessarily The Same - 08/25/05 Good day Crew!! <<Howdy!>> Thanks for the site, the bountiful archives, and the appreciation of proper grammar. <<You been talkin' to Bob? <G> >> I admire and appreciate what you are doing for me, and the rest of the (would be) marine aquarium keepers out here on the world wide web.  Good work, people! <<I/we enjoy/believe in what we do, but still...redeeming to hear...thank you.>> Having said that, my question to you is, how many times an hour should I turn over water through my sump vs. through a closed loop system? <<Two to three tank volumes per hour through the sump...ten or more (preferably!) tank volumes through a closed-loop.>> I know the recommended turnover is 10x - 20x an hour, but does it all need to run through the sump where the filtration will be? <<Nope, nor do I recommend/think this to be practical.>> Or can I just run my water, say, 5x - 10x times an hour through my sump (and all of its various components), and the other 10x - 15x in a closed loop? <<Could...though I still think that's more than you need going through the sump.  Less flow through the sump will be easier to plumb with less hassle/subsequent noise.>> Is there an ideal ratio? <<Every system/configuration is unique, but the basic flow rates I listed should work well for most.>> I can't seem to find the sentence that says, "An aquarium should be completely filtered XX times per hour."  (Assume I would like to keep delicate and demanding species, for which flow seems to be most important.)  Naturally, more filtration is better, but I have concerns about my setup, and if I am going to be limited by flow through filtration, I would like to know now, so I can stock to accommodate it (or modify the tank to suit my needs).   <<Flow and Filtration are two different things.  Besides, if we're talking a reef system with live rock, most of the "filtration" will be going on "in the tank" where, yes, your "flow" needs to be random, turbulent, and robust (e.g. - 10x-20x tank volume).  2x-3x tank volume through the sump to supply the skimmer and maybe some sort of chemical filtration will be just fine.>> I recently acquired a used 125 gallon setup.  What was included was the tank, stand, and a canopy equipped w/ 3 175w MH bulbs (and room for some 72" tubes).  The tank is predrilled, in the bottom, with a 1 3/4" hole in each back corner, and of course, with overflow boxes installed (glass).  If I am correct, these holes will accommodate 1" bulkheads, both of which I plan to have drain to a 55 gallon sump. <<yes>> (I think I am correct that the flow out of the display through these bulkheads can be regulated by the return pump, but I am afraid that due to the small diameter of the bulkheads, even at max, I will be limited.) <<yes again>> By the way, what kind of flow can I expect through each of these bulkheads?  I think I read 300 gallons for return bulkheads, and 800 gallons per hour for drains.  Is this right? <<I would plan for no more than 300-350 gph per drain to the sump.  This flow rate will ease any plumbing issues when it comes to eliminating noise, and provides some measure of safety margin in the event of a blockage.  In fact...I would recommend plumbing only one drain to the sump (approx. 300 gph submerged return pump), and use the other drain to plumb your closed loop (1500-2500 gph external pump).>> The return will go up and over the back of the tank, as I have seen recommended several times in the archives to people in similar situations. <<okay>> Since this whole thing is still in the planning stages, I am hoping this input (and a lot of input found in the archives), will save me heartache and expense, as I do plan to stock only with captive propagated (hence, more expensive) species. <<Always good to have your stocking plan before you build the system so as to tailor to the organisms needs.>> I don't advocate loss of life or destruction of reef under any circumstances, so I am going to thoroughly do my homework to accommodate any species I consider for captivity in my home, based on what my system can accommodate. <<Or...research/pick the species and build the system to suit...>> I absolutely will not house an animal that would otherwise have a home, and will only house one that will be happy in my home, i.e. there is probably not an anemone in my future. <<Very good to hear.>> I am the same way with dogs, getting them only from the pound. <<Admirable...but as you say...only if you have the means to provide...>> Also, I am quite determined to do this myself, much to the dismay of the LFS owner, who would just love to come set this up for me.  However, I am afraid that he would abuse my pocketbook, and betting on my ignorance, some innocent marine animals, and I can't do it.  Besides, I like the challenge. <<Quite within your abilities I'm sure...just be sure to stop and think, research, ask questions as you are now, and above all...take your time.>> Thanks for all of your help and expertise that I have already made use of, and will use in the future.  I am looking forward to being an informed/conscientious marine aquarist (great book, by the way). Sincerely concerned about adequate filtration, Jessica Groomer <<Please do write back in/make use of our extensive archives re tank setup/close-loops.  Regards, EricR>> Water flow reducing nuisance algae 7/6/04 Anthony: You asked me to send an update on how things went with my algae problem after your advice to increase my water flow. I think you were correct. After a month of tripling the original flow in my 75-gallon tank, I still get a patch of red algae here and there and there is some hair algae, but it's not nearly what it was. It's very manageable now <ah, very good to hear. You can polish off the rest of it likely with more aggressive skimming and tweaking your feeding regime (smaller feedings, more frequently if needed) and being tidy with feeding habits like never adding thawed pack juice from frozen foods into the aquarium (always thaw froz. foods in cold water, then strain meat away for feeding... else the pack juice is rocket fuel for nuisance algae/nitrates, etc.)> (a toothbrushing here and there every few days) and I suspect it will get even better as I refine my flow system. I'm embarrassed to say that when I first wrote about this problem, all my water flow came from my return pump, probably about 450 gph. <wow... remarkably slow/low> Now I've got four power heads totaling 1,340 gph in the tank. What a difference. The fish and corals seem more healthy too. <indeed more natural> Here is my next question: I'd like to get the power heads out and replace the return pump so I can use the PVC ring setup that goes around the top of my tank for all my water movement. (It's 1/2" PVC with eight openings that is currently supplied by my small Little Giant pump.) <very good> However, I'm afraid of flooding the tank. I have two 1" holes in the back of the tank. One is now used to link the return pump to the PVC ring. I figure I can switch that to a second drain and then just plumb the new return pump directly into the PVC ring that runs around the top of the tank. However, I can't seem to get a consistent figure on how much water 1-inch holes in the back of a 75-gallon tank can handle. <they say up to 600 gph at a noisy running siphon level... but that is dangerous. Frankly, Id count only about half as much: 300 gph per 1" hole max> I would really like to do it this way both for aesthetics and because I could better direct the flow to all parts of the tank. But I really, really don't want the worry of possible flooding. <rather than be at the mercy of your drain holes as a rate limiting factor, why not feed the PVC ring manifold with a pump from inside the aquarium? this will be independent of the return pump on the sump and as such have no influence. No chance of flooding for it (they are unrelated). You can get some very small pumps that push a lot of water (like those submersible "silent ones")> (In fact, I've thought of just buying a large, fish-safe powerhead, like a big Rio, and running its output directly into the PVC system. I'd still have a powerhead in the tank, but I wouldn't have to worry about overflow. <I should read ahead <G>... yes, exactly> Plus, I'd probably get a little more power from my Little Giant pump by disconnecting it from the PVC ring and letting it return directly into the tank.) <no worries... you can get submersible pumps for this that far exceed the Little Giant of choice here and are more than you need> Questions, questions. Sorry this is so long. Again, you were correct about the water flow and I greatly appreciate your advice. Matt <best of luck, Anthony>

- Circulation and Diatom Blooms - Dear Bob, Jason C., or whomever: <JasonC again... greetings.> Just wanted to thank you for your reply to my recent questions.  My 180 gallon marine tank is now up and running and so far all is going well.  I do however, have a question or two about a light brown coating beginning to appear on the sand substrate.  The tank has been running now for about one week, and the sand substrate has finally settled down and the water is slowly clearing.  However, a light brown film is developing on the substrate that I will assume is a diatom outbreak. <You are correct.> I am surprised by this because I have taken every measure known to prevent this from happening. <Not necessarily 'preventable' but often the first part of a series of succession... to be followed by other green algaes. Likely you were not able to rinse the new substrate as well as you might have thought.> Please note that this setup imported about 30 gallons of water and roughly 50 pounds of mature live rock that I had from another tank that I broke down and sold.  In addition, the new water is 100 percent RO/DI water mixed with Tropic Marin salt, an additional 110 pounds of live rock was purchased cured and hand-picked by myself, a Euro Reef CS8-1 Skimmer has been going from day one, a filter bag with Phosguard is being used just beneath the water return in the sump, and the water flow in the tank itself is more than adequate with two strong return flows from the Mag 18 pump and two additional MaxiJet 1200 powerheads. <I would at least double this number... in a 180 you could put a half dozen of these and still have dead-areas with little or no circulation.> Three fish (a purple tang, pygmy angel, and Scott's fairy wrasse) were brought over to this tank from the aquarium I broke down.  I ran a series of water quality tests and all seems well:  1.0238 specific gravity, 8.1 pH, 9 Dkh, 0 ammonia, 0 nitrite, 5 nitrate.  Here are my questions:  If this is a diatom bloom should I simply ride it out and not be too concerned? <Is what I would do... am doing, just moved from one tank to another myself and am experiencing similar circumstances.> There are no corals in this tank, only live rock, some mushroom anemones, and the three fish.  Should I reduce the photoperiod? <Will have some effect.> Presently, I run 120 watts of actinic fluorescent from 12 hours, and 192 watts of power compacts 50/50 Smartlamps for 10 hours.  Adding additional flow to the tank seems unnecessary, and if the water flow is too low the sand gets disrupted and sent into the water column. <I would disagree... having been diving on only a couple of reefs, what is immediately obvious to me is that there is no practical way to have 'too much' circulation. Most reef fish are accustomed to circulation rates of tens to hundreds of millions of gallons per hours... sometimes per minute.> I was considering a couple of the white sand sifting starfish, but I'm not sure how many for a tank of this size. <I'd skip these and instead get your hands on some Nassarius snails.> Are these worth the investment? <Not in my opinion... will destroy much of the useful fauna in the sandbed.> By the way, the rock and glass do not (yet) show any signs of this growth, so I'd like to keep it in check right now if I can.  Any suggestions? <More circulation.> Thanks for all of your help.  Sam M.   <Cheers, J -- >

Cyanobacteria/BGA and circulation - 2/14/03 To whom it may concern  :o) I've read the posts about controlling BGA by eliminating dead spots and improving circulation in your tank, so I tried a little experiment:  I had one silk plant (deco) in my tank with some Cyano on some of it's upper leaves - about the only presence of BGA in my tank. Anyway, I aimed a powerhead right at it and blasted it until the flow forced it to bend double and almost touch the substrate - kinda like it was caught up in a tornado - anyway after a week of this, guess what?  The Cyano actually increased!! What gives?? <DOC levels, phosphate and nitrate levels, lack of water changes (large enough), allowing thawed pack juices from frozen foods into the aquarium, lack of adequate chemical filtration (weekly/monthly carbon), weak skimmate (light color or volume).... Nutrient control overall, aging fluorescent lights... all valid catalysts> Xeo <Anthony>

Getting Off To A Good Start (Pt. II) You mentioned powerheads for more circulation.  Why to I need extra circulation? <Circulation will perform several tasks in your tank. First, it provides extra movement that will keep detritus in suspension, where it can be picked up by your mechanical filtration. Also, it will help provide more even temperature and chemical parameters within the system, by "mixing" the water. If used with an aerating feature, you can also increase oxygen levels in the tank...Currents also help keep fishes active and strong...You'll see a definite increase in activity if strong currents are provided!> Also, about the live rock: How long should I keep the lights on if I use it? <I'd keep a "normal" day/night schedule...At least 8 hours of light would be fine...If you have photosynthetic life forms on the rock, they will benefit from the regular photoperiod> What does "cured" live rock mean? <"Cured" live rock simply means that many of the organisms that reside within the live rock, which often die during the shipping process, have decomposed completely, to the point where no ammonia is present in the water. Once this process is complete, the rock is considered "cured"> Do I wait until the tank is completely cycled to put it in?  And since it contains living things won't that contribute to added ammonia and nitrite levels? <Yes, the animals (living and dead) will contribute organics to the water. I prefer to cure live rock in a dedicated container, in which regular, massive water changes and detritus removal can easily be accomplished. When curing is completed, as evidenced by undetectable ammonia levels, and no stinky smell (trust me- curing live rock STINKS!) is evident, you can place it in your system. Remember, there are many different ways to cure live rock and cycle systems, so do a little reading on the WWM site, and use the technique that best suits you!> Thanks again, James <My pleasure, James! Good luck! Scott F>

Water flow and Algae Anthony you and I have talk about water flow in reef tanks, and you have said many times about having outlets on all side of the tank.  <yes... not written in stone but nice for many aquarists trying to achieve random turbulent flow without investing much time or thought into the process> In my own 180 gal reef tank I pump 2000 gal per hour out of 4 outlets in the back of the tank. But if all reef tanks large and small had also 2-4 outlets in the front of tank it would keep algae down much lower then they have now.  <agreed> Keeping algae moving would give the p skimmer a better chance to remove them from the tank.  <exactly... detritus stays in suspension for removal by skimmers, etc and the algae themselves are often inhibited by reef type flow... they generally favor calmer waters (warmer temps and higher nutrients too of course)> "Dilution is the solution to pollution" <Amen!> Have a good day RGibson <kindly, Anthony>

Re: New Hobbyist Do you think I need any form of aeration other than my Red Sea protein skimmer? <Likely not as long as you also have vigorous circulation.> I am storing my sea water. I just have the water in buckets. Is it necessary for circulation or other things? <Aeration and heating to match the display is needed. -Steven Pro>

Re: Make up water  One dumb question. Won't good circulation provide good aeration?  <not a dumb question at all but also incorrect (a common misconception). Aquarists with overstocked fish tanks and undergravel filters know this: powerheads with venturis off lead to gasping fish behavior... turn the venturi back on and the O2 saturation increases and fish are relieved. Circulation of the system from top to bottom does help, but aeration from a skimmer or aspiration (venturi) of air through a pump is better> I mean, if I have good circulation (I have two 295 GPH power heads and my return is a 3MDQX 875 gph @ 6', and I am pushing up only 5' and it's split into three outputs at the tank) a total of about 1500 gph and I run my Berlin skimmer with a mag 7 pump 24hrs/day, will this not provide good aeration?  Sure... good, yes. But enough, I don't know. The simple test that I mentioned before will clear this up. If a vigorously aerated glass of water gives a higher pH reading then when you started... you do have a slight problem with accumulated CO2 (easily corrected with increased aeration)> I will try your suggestions below, thanks for your patience! Larry <my pleasure, bud. best regards, Anthony>

Extra water movement Hi Bob, just a quick question. This probably sounds like a stupid question. I have just bought a Juwel aquarium with the filter system. <Great tanks... have been a big fan for decades> Is this enough on its own to put enough oxygen in to the water , there are no bubbles being put in the water and I am worried that it is not working or am I just being stupid. Thanks in advance, Malkyb.... <No problem with adding a bit more aeration, circulation. I would add a powerhead or three, depending on the size of this tank. Bob Fenner>

Small system circulation questions Greetings again Bob, <Hi there> This is probably a really dumb question and it shows just how inept I am in the whole aquarium area.  <Don't discount the validity of starting/stating at this point> I thought (and you affirmed my suspicions) that I should put a powerhead in my eclipse 12. (I have an airstone strip thingy along the back and the damsels seem to have adjusted quickly to the bubbles :) So powerheads... all the ones I've seen say that they are made to attach to undergravel filters. is it o.k. or is there a way to use the powerhead without an undergravel filter? <Yes. All models are able to be modified for this purpose... look to using a sponge on the intake if provided, at least a "Bioball" on the intake if not> and do I leave these things on all the time? <Yes> where would be the optimum place to place my powerhead, or does it depend on where I plan to put corals and such? <To some degree... in such a small system it is fine to just aim the discharge in such a fashion to increase/optimize overall circulation> Thanx again, Ben <You're welcome my friend. Be chatting. Bob Fenner>

Become a Sponsor Features:
Daily FAQs FW Daily FAQs SW Pix of the Day FW Pix of the Day New On WWM
Helpful Links Hobbyist Forum Calendars Admin Index Cover Images
Featured Sponsors: