Does everyone really have 10x-20x flow?

[bluewhale]

I've been keeping reef tanks for eight years and just found this site recently. It's great! But some of the information is making me doubt my reef tank husbandry!

For example, the consensus recommendation for a good rate of water flow in a reef aquarium seems to be 10 or even 20 times or more the volume of the tank per hour.

I recently moved to a new flat (apartment) and got a new tank built. It's been up for about two months now. The display tank is about 500 L (130 gallons) and the sump is about 180 L (50 gallons). After I got two new Eheim 1262 pumps to use on the returns from the sump (to replace two lower-volume pumps), I removed the powerheads (Tunze wave simulators) from inside the display because they were ugly and I thought that, with the new pumps, the water coming from nozzles near the top of the water column was creating quite a lot of nice chaotic flow, with some fast current areas and some slow flow areas. To give you an idea, in the fast areas a medium-sized yellow tang (Zebrasoma flavescens) has to work to work to swim against the water and finds it difficult to hover in place but can still do so. Everyone seems happy -- SPS polyps are extended and they're growing, chemistry has been fine. In fact, no problems with the new tank at all so far.

Well, after all this web site browsing, today out of curiosity I measured the flow (which now comes only from the returns from the sump), and it came to only around 2000 L (500 gallons) per hour, or about four times the volume of the display tank, due to head pressure from the piping.

I know that guidelines for things like flow rate are just rules of thumb, and obviously I will go by the condition and behavior of the livestock, but is there any compelling reason I should I put the powerheads back in? Would more flow make things even better for SPS? Will I find that dead spots will one day make diatoms bloom like hideous brown fireworks overnight? Or is there a conspiracy among aquarium equipment manufacturers to get reefers to buy (even) more equipment!?

Any advice would be greatly appreciated!

 

[les]

Welcome to the forum.
I think that what alot of people try to recreate is a high energy reef top. Now that being said even though some of us try real hard to achieve that we still fall well short. There is no way to truly simulate the power of 10 foot or larger waves crashing on a barrier reef.
I actually have in my tank about 45 water changes per hour. I can say that everything is growing likes weeds also.

 

[bluewhale]

Wow that sounds like one high-energy tank.

I'm a scuba instructor and have seen quite a few reef tops over the years. I can't say that the ones in five knot current or in a surge zone are any more beautiful than the ones with 0.5 knots. But that said, one knot is 20 inches per second, which I guess would be similar to what we get from powerheads.

 

[wrightme43]

I got 52x per hour. Seems to work well.

 

[bradreef]

I would like to up mine to 100x but it has to be done right.. flow is good.

 

[bluewhale]

I'm not sure I get how this works. How do you calculate the number of times?

I guess it would not be physically possible that you just account for the volume of water that goes through the mechanical filtration system. So do you add the volume that goes through the power heads? If power heads count too...

- Do you account for the length of travel and the deceleration over linear distance? (That is, right at the power head it's 100% of the pump's capacity, at 1 foot you get credit for X%, and at 2 feet you get credit for Y%, etc.)

- How about the loss of momentum when the stream bounces off glass or rocks?

- What about the cancellation effect when water flows travelling in opposite directions or at angles hit each other?

I'm really confused. It seems that unless you have the water going around in a circle like a tornado, there would be a certain point at which you can't get any more total movement no matter how much more power you add.

That being the case, the only way to get the water to travel faster at any specific location in the aquarium would be to get a more powerful single source right near that point. If so, what's the point of having the ratio for the whole aquarium?

Thanks for your expert advice!

 

[big t]

Basically most people don't look into it that far. Someone like me will say that I have 46x water volume turnover, that means that I have a 90 g tank w/ a 3000 gph closed loop and 1200 gph return pump. Then if say Steve had the exact same setup but he figured it for head loss the steve says that he has 37x water volume turnover. I was down at a famous local fish store in Portland Oregon, it was a 180g tank w/ no powerheads, no closed loop, w/ 2 mag 24's feeding the returns from the sump, he said he had 26 times turnover (he had no where close to that, but the tank was one of the most amazing I had ever seen) Then there are those like Nikki, she has pretty much the same pumps as me but a slightly larger tank, so she has about 30 times turnover, but she has a industrial 3 way ball vavle silenoid that switches her current from one side to the other, at a interval, so does she have more like 60 times turnover? A lot of what you read is the users interpretation. Most people take all of their pumps that add flow to the display, add them up and divide by the tank size. Sorry for the ramble.

 

[bluewhale]

Interesting. I guess it would be much more useful to look at the turnover of the aquarium through the sump or other filtration system (useful to know for filtration). Then directly measure the localized flow in different parts of the aquarium with a sea current meter (useful for getting the right knots of simulated current for animals, or the right velocity and variation in Nikki's case).

Bruce

 

[big t]

That sounds interesting. I the key that most of us over here are trying to do is to reduce dead spots to a minimum, to prevent detritus collection and buildup. If you can do that it helps prevent the growth of nuisance algea. I have found that w/ aprox 40 times water turnover that I still get a lot of detritus built up in the rocks, and lots in certain spots in the floor, so I am still stuck w/ blasting the rock a couple times a week w/ a powerhead to free it up and make it available for coral consumption and skimmer removal.

 

[bluewhale]

That's what I do too. Last month, I was really stoked to come across a completely submersible hand-held vacuum. (The shop clerk probably thought I was crazy I looked so happy.) So now I turn off the pumps, blow things around with a powerhead, and suck out the piles of heavier gunk from the bottom. (The bottom is just glass. No substrate.)

 

[wrightme43]

Ok how I figured mine is my tunze is 3175 gph. It is on a multi controllor I figure its on full blast half the time and making 2100gph the other half. Its set well over halfway on the second cycle but not full blast for a average of right at 2650 gph really 2637 but close enough. I have a 1506 gph return pump. I figure with head loss and elbows I am seeing about 800 gph at the seaswirl. I have a eductor on the sea swirl. I know it is not working to total effect but it is helping to increase flow some. So I figure it does conservitivley less than double what it would with out it. So I figured 1250 gph flow from the seaswirl eductor combo. That makes 3900 gph average flow in my small 75 gallon tank. That is 52 times tank volume turnover per hour in flow. What it has done for me, is that my acros have really increased their polyop extension and its really cool to sit and watch them wave one way sorta stop at the tunze and the seaswirl do thier crossing and opposing and assisting flows which is constantly changeing because the seaswirl is rotating back and forth while the tunze is ramping up and down. Its pretty super cool if you asked me. LOL
Steve

 

[bluewhale]

That is cool! The ones I removed are also Tunze variable rate pumps. I'll think about putting them back to see what happens.

After years of adding more and more equipment, I am now trying to simplify to get back to basics and reduce maintenance for my new tank, but maybe I have gone too far with the pumps!

Now I have no corals or anemones that need feeding, no sand, no refugium and no potentiometer, am doing more frequent and bigger water changes instead of supplementation, and am even using cotton-like filter pads (gasp!) to catch organic matter. (If anyone wants an electronic salinity meter, let me know. I'm happier with my glass hygrometers!)

Bruce

 

[clayswim]

I have 22X on one and 36X on another. The Tunze pumps work great because they create lots of flow without the jabbing tight jet stream that most powerheads and pumps create. The idea is to move water, not give our critters a massage.

Clayton

 

[richard55]

I have a seio 1100 and a seio 620 in my 55 so not counting the HOB filter and skimmer I have 32x the flow.

 

[bluewhale]

For all the devotion I see here, we might as well be giving them massages... and sending them on spa holidays in Bali. ;-)

Clayton, know what you mean. Once I had a powerhead flow being deflected by a rock and a tang got pinned and died.

I still think it would be more useful to measure flow in local spots in the tank, instead of talking about overall flow that gets changed and reduced by all sorts of different factors. (That's what I do with lighting strength. I measure it with a submersible light meter, and you'd be surprised at the variance not only from water depth but from shadows.) Does anyone know of such a device for measuring flow? The ones they use in the ocean are obviously too big for aquariums. I guess you could get a good idea by watching floating stuff in the water, but it would be better to get accurate, standard readings that are reproduceable.

 

[richard55]

I dont think that measuring the flow would matter. How would you manage this it would be different at every point in the tank. The idea as I see it is by turning over the water as much as we do we cause the water to exchange gases from the tank to the air and we move waste back into the water to be removed by the filtration. The other reason for a high flow in a reef tank is to move food to the polyps so the corals may eat. Comparing our tanks to the ocean is "nice" in theroy but a waste of time for the most part. In the ocean a reef may get a lower flow and still be healthy, in our "CLOSED" systems we must work around the limits of the volume of water and our ability or lack of to maintain water parameters and food levels.

 

[bluewhale]

I totally agree on your points on the importance of having flow.

I did mean to measure every point in the tank, actually, or at least the parts that matter. The purpose would not so much be to simulate nature, as to have a standard measurement. Now we can say that, in an aquarium, a species likes the water temperature between X and Y degrees, and light of this spectral frequency and that number of lumens, and it can withstand pH of such and such a number. So if we could measure local flow, then we could say a species requires current flow of a particular range and reproduce it in different tanks. (That's what I meant by reproducible, by the way, not reproducing the ocean.)

Just to be clear, this measurement would not be a substitute for an estimate of flow throughout the whole tank.

Bruce

 

[richard55]

So what your getting at is at the acro you have x gallons per hour, at the clam it is x ect... that is cool.