Flow rate

[dotzkill]

I've tried looking an I can't really find anything on this but to calculate from what ive read is you take all the things in your tank that moves the water. So lets just go with my tank.

1 power head 425gph
1 power head 240gph
1 aquaclear filter 200gph
--------------------------
which equals 865

now devide that by my total tank water which is 21.9 gallons

which is 39.49

is 39.49 my flow rate?

[Levito]

I believe flow rate is how many times the water in your tank is cycled in an hour. So your calculation would be correct, and that means you have a ton of flow. I believe the general rule is you want to have at least a flow rate of 10. Above 20 might be overkill, but I'd be interested in hearing other people's opinion on whether or not to cut down on the flow.

[The_Codfather]

In the US people tend to like 10 or so .. In Europe it tends to be lower

[nvdiz]

Your math is correct!

For Levito and Codfather, flow rate depends on the corals you keep in your reef. I have about 70-80 total turnover in my sps tank

[reeferx2]

Around 60x for me in an SPS dominated mixed reef. I would say 10 times an hour is a bit low. I think the 40x an hour you have should be fine. Depending on your corals you may need a bit more or less.

[tozzi]

Flow rate through your sump or filter is different than the total flow in your tank. The "turnover" of a tank would be the flow through the sump or filter. Wich is usually about 4-7x your total system volume an hour. When people talk about 30 40 50 x an hour , thats a combonation of your return pump and all the pheads and wavemakers in your display. The "total flow" i guess you can call it, in your tank

[ChadTheSpike]

flow rate equals volume per hour, that is it. In other words, gallons per hour (GPH) is flow rate.

Various devices that add movement to the water contribute to the flow rate. So, in your case, you have 865 gph of flow rate.

turnover = flow rate / tank volume = number of times your water volume turns over in an hour = mostly a useless number, but does give a general 'feel' for how much flow one has.

The part that is different that you all are not talking about is flow velocity = distance moved per second. This number is difficult to measure in water, and is mostly impossible for the average reefer to measure it. The same flow rate can apply to an infinite number of velocities. 100 gph through a 1/2" nozzle will be significantly faster (velocity) than 100 gph through a 2" nozzle (which would hardly be noticeable), but the flow rate is the same.

So, long story short. Your flow rate is 865 gph (actually less because of head loss), your turnover is ~40, and your velocity varies throughout your tank.

[tozzi]

The part that is different that you all are not talking about is flow velocity = distance moved per second. .

Is this something new? Never heard of it before. i've heard of a flow accelerator? But it doesnt reduce the opening size, it uses an air gap to increase flow And there is a difference between the amount you turn your tank over [ through a sump, skimmer, or filter]. And how much flow you add with a powerhead, wavemaker, or closed loop, because these do nothing to filter the water. thats the difference.

[Levito]

Your math is correct!

For Levito and Codfather, flow rate depends on the corals you keep in your reef. I have about 70-80 total turnover in my sps tank

Wow, I never noticed people had that much flow. Thanks for pointing that out. I wanted to start adding some sps to my tank, I guess I should increase the flow? I've currently got a flow rate of ~15 in my tank (~1000gph in a 65G tank).

[ChadTheSpike]

Is this something new? Never heard of it before. i've heard of a flow accelerator? But it doesnt reduce the opening size, it uses an air gap to increase flow And there is a difference between the amount you turn your tank over [ through a sump, skimmer, or filter]. And how much flow you add with a powerhead, wavemaker, or closed loop, because these do nothing to filter the water. thats the difference.

No, it is nothing new. It is just difficult to measure (can be done by particle movement, but that is tricky). Since it is difficult to measure and visualize, it often isnt, and many use the term flow to mean velocity which doesn't really work.

When you talk about flow accelerators, do you mean eductors? An eductor works on a different principle and raises flow (and sometimes velocity) by entraining fluid around the nozzle (that would be stationary without the holes) into moving and constricting the throat of the nozzle to raise velocity.

How does filtering water have anything to do with flow? Flow is just a volume of water moving. Velocity is just how fast that water is moving. The device that makes it move doesnt matter because a volume of water is still moving. To put it into math terms, flow rate = area times velocity. In terms of our tanks, the flow and velocity produced by a skimmer is usually returned to the sump, which does not affect the tank, but it could if it were a HOB skimmer.

My point is that turnover is a useless term as it doesnt say anything about velocity, which is important. Look at it this way, if you have a 10 gallon tank and one 100 gph pump it is very different to have all of that flow directed through one nozzle directly onto something than it is to have several nozzles dispersed over the tank. Another example is if you have the same ten gallon tank that is dumped out and refilled once every 12 minutes. All setups have a turnover of 10 times per hour, but they are very different and not really comparable. Besides, what is the turnover of the ocean?