Waterflow - once again - how much is enough?

How much water volume turn-over in your tank (litres/hour)?

  • 0 to 9 times turn-over

    Votes: 2 8.3%
  • 10 to 24 times turn-over

    Votes: 3 12.5%
  • 25 to 49 times turn-over

    Votes: 9 37.5%
  • 50 to 100 times turn-over

    Votes: 6 25.0%
  • more than 100 times turn-over

    Votes: 4 16.7%

  • Total voters


Retired Moderator
29 May 2007
Reaction score
Cape Town
Hi All.

Regarding water-flow: How much is "TOO LITTLE", "ENOUGH" and "TOO MUCH" in a reef tank???

What are the numbers (total litres per hour) of water turn-over that one should look to achieve in certain sizes/types of tanks? (whether this is achieved using power-heads, closed-loop systems, sump return pumps/pips, wave-makers, etc....)

How about a poll on who have what amount of water-flow in their tanks? (total water volume turn-over), and how do you achieve this? (in-tank power-heads, closed loop systems, sump return pumps/pipes, surge devices, wave-makers, timers, etc.....
I think we musty move away from the litres per hour turn over. Personally you need to look at what you want to keep and go according to that. I have up to 30 000 lph at max flow on my 6ft 450L setup. Good for my sps, leathers and my nenny. Too much for some of my LPS(Need to block water off with aquascaping).

The 100x turn-over is in the same lines as the 5w per gallon rule. Some people achieve more with 10x turn over than others will achieve with 50x turn over.

My personal opinion is random turbulent flow, such as the flow you will get from a proper surge box/device.

My 2c
I have to agree with cybervic here, personally i have just slightly upgraded my flow i removed the . 4000l seio's and replaced them with 6000L. I now have my return pump rated at 8000L but with the head it is about 3000L, my 6500L closed loop with head loss about 4000L and 4X 6000L seios. Only 2 of the seio's run at any given time and find i have plenty flow in the tank. reading your other thread Jacque instead of bouncing the flow off the back wall aim the pumps the full length of the tank, thus moving the largest water volume possible and try alternate the flow from left to right and then right to left and a short burst with both on to really mix things up. Thats how i have my seio's pumping at the moment and dont have any problems with detris or algae.
Cybervic - so if I understand you, Alan and Regal correctly - this is like with EVERYTHING else in this hobby - there are no HARD and FAST rules regarding the flow rate in one's tank. Every one elses setup is different, and require different flow rates???

This seems to be the most logical deduction I can make of this....
I would its along those lines with heavier flow required for SPS corals.
Another related question - Alan, perhaps you can answer this - have anyone experienced that you have very high turbulence in the upper half and centre of your tanks, but not in the most left and right hand corners?
Causing "dead-spots" in the corners then?
This is why i suggest to try move the water across the tank L-R and then R-L and then converge in the middle. Might get rid of the dead spots at either end.
- have anyone experienced that you have very high turbulence in the upper half and centre of your tanks, but not in the most left and right hand corners?
Causing "dead-spots" in the corners then?
i have that problem,although i have a 58 times turnover.gonna do what Alan has mentioned.
Hi Alan/Mekaeel...

Here's some ranting from me, on a similar thread on the "other marines forum":

Cool! Many thanks for the informative comments. And yes - I agree with the surges, and diving on the reefs. I know what you guys mean.

BUT just to play "devil's advocate" here - we are talking about flow in a VERY confined space - whereas with real coral reefs out in the sea, there's this AWESOMELY HUGE body of water, moving in a constant rhythm (surges), which only picks up pace EVERY NOW AND AGAIN, when there's a terrible tropical storm which churn's up the water, where this rhythm is disturbed and an immense amount of turbulence is caused. BUT, this only happens every once in a while...... You see, what Terrence in Cape Town has done, is to nearly simulate such conditions, with a constant ebb and flow of the water in his 3.5 meter tank (being created by 6x Tunze powerheads on specialized timers which together as a one (the one side at a time) switch on, and then the other side's pumps switch on...... something like what Alan's trying to achieve.....

This is not a constant turbulent environment - the real reef environment.... There is NO WAY that you have such an immense amount of water flow, constantly, 24x7x365.... You have a constantly changing environment. With the reefs being brilliantly peaceful with barely ANY currents or even much diluted ebbing and flowing, and the next day a absolutely cyclonic environment where the sand is being kicked up, the corals being broken off, etc. etc.....

That's the "real thing"..... Now what to do to simulate this in out tank environments??

By the way - now that I think about this - it would actually be REALLY impossible to recreate a "real reef" in a closed environment such as our aquariums.....

So we supply an artificial environment to life-stock which are actually highly adaptable, taking into account the amount that ANY aquarium differs from the "real thing"......

So, I think that it's once again a matter of acclimatizing OUR life-stock to the aquarium environment they are supposed to life in. They sort-of adapt - some adapt better than others.....

Taking into account some reef aquarium tanks that I have seen on the internet where the people don't use calcium reactors, barely any excuse for skimmers, BARELY ANY power-heads in their tanks, the different types of lighting, the hugely different levels of nutrients in the people's aquariums...... AND there are some STUNNING aquariums out there, which would hugely adept by "our" standards.......

Just to finish off my ranting: Yes - I will try and make do with what I have at the moment, and YES, I will try and upgrade/improve the flow in my tank - BUT, IN TIME - as everyone always says - TAKE IT SLOW - ONLY BAD THINGS HAPPEN QUICKLY IN A REEF AQUARIUM. I have NEARLY doubled my flow at the moment from previously, I WILL most likely give my life-stock some time to adjust (a few months or so), and then UPGRADE again (get some more ReSuns) to try and double the flow in my tank AGAIN.... BUT only in a few months time......

I understand at what you all are getting at.... and I think that the main concept here seems to be: try and ensure that there are NO dead spots in one's tank - however way you achieve this......


What's your opinions of this?

Anyone else??

Many thanks.
(and apologies for those who belong to both forums - who have read this twice)...
I don't think you have insufficient flow at the moment, just try angle the pumps so that you achieve the best results. I fully agree we cannot simulate our tanks to what happens on a reef [unless you want to keep a whale in the sump] and yes the animals we keep are very adaptable to our conditions. The only thing i try achieve is random flow in the system and use the pumps as effectively as possible.
Okay, just re-read your ranting on this thread and this is my take on the whole issue. The hobby we are involved in is constantly changing and our focus is constantly shifted, from skimming to lighting to water flow etc... etc... etc... Now no matter how hard we try we will never simulate the ocean in our closed systems we can only provide the best conditions we can. No matter what the latest rave is there is not only one aspect of the hobby that will make you a successful aquarist, you have to view the overall picture. At the moment it seems like water flow is the flavour of the month but is not the be all and end all of a successful reef, as you stated there are tanks out there that seem to have very little flow and are successful. As a hobbyist you will have to learn to read your system and find out what its needs are. The only corals on a reef that have that very turbulent flow all the time are the ones in the upper reaches where they are in the path of wave action, so is it necessary to have 6 pool pumps connected to your 4ft to simulate this IMO i don't think so. The movement we create in our systems is basically to carry waste away from the coral and bring in fresh water for the coral with enough movement to keep waste suspended to reach the skimmer. There are very few systems that don't have any dead spots at all, so don't sweat too much about that. One of the most awsum tanks i have seen is Glynn Foremans tank and considering the size of the system there is way too little flow but look at it and look at the growth he has, there are no hard and fast rules here.
I have been following some of your posts over the past few weeks and it really seems like you are getting to grips with the overall picture, all i can say is trust your own instincts as to what your system really requires, we can only offer advice on the boards but you are the person that knows your system inside out.
Top Bottom