Calculating Water Turnover

[darthgoby]

I've heard that a reef tank should have a certain level of water turnover whereby the water turns over the in tank a certain amount of times. I've had that it should happen about 10-20 times per hour. In other words, since I have a 55 gallon tank, I should have between 550 and 1100 gallons per hour.

What I"m not sure about is how to calculate that and what factors into the turnover calculations. Here is how my tank is set up:

1.) I have a refugium pump that pumps about 300-400 gallons per hour into the tank
2.) I have a protein skimmer that does about 300 gallons per hour
3.) I have an overflow that takes out about 300 gallons per hour. I'm assuming that it's 300 since my refugium pump is more or less matched to my overflow.
4.) I have 2 powerheads. One is rated at 400 gallons per hour and the other 100 per hour.

If I add these up, I get about 1400 gallons per hour or a turnover rate of 25X per hour.

Is this correct or am I doing this all wrong?

 

[rdfriend]

I would think that the overflow value would already be in the refugium pump since it is in that loop. If you feel that pump is running close to max. and you add the powerhead values you are probably closer to 1100gph. If you are getting good coverage in the tank it is probably enough but might want to increase if you have corals or dead spots.

 

[Fishieness]

you arent going to want to calculate the 300 for the overflow if you are already counting the 300 from your refugium. So with that, you have about 1100 gph which gives you a 20X turnover rate, estimated. However, i have another question; your refugium pump pumps 300 gallons per hour? Is that normally or does that factor in any height difference between the sump and the refugium? For instance, a mag3 will pump 300 gph, but not if it has to travel up 3 feet and has a few 90* elbows, the thickness of the tube, etc. If that is the case, you probably have around an 18X turnover rate.
Turnover rates in reef tanks vary depending on what you are keeping and how your tank is set up (how the powerheads are positioned in eliminate dead spots, weather or not they are working with or against each other, etc). Many types of corals like low flow, others like very high. Some NEED very high. I am a personal fan of a lot of flow and wouldnt personally run a tank with that low of a turover rate. many people suggest at least 20X. But like a lot of people keeping sps, i have much more than that. Here is what is in my tank:
10 gallon tank:
-maxijet 1200 return from the sump (pumping an estimated 200 gph with the head loss)
-mini-jet pumping 106 gph
-random other powerhead running 50 gph
-hydor koralia 1 running 400 gph
this gives me a 75.5 times turnover rate
and that is one of the lower amounts i've had on my tanks.

I would personally add more flow.

 

[fsn77]

Typically, the pump on the protein skimmer isn't counted in turnover rate. Some people do not include the return pump that moves water from the sump / refugium back to the display tank, either, as it tends to be a small amount of the total. That said, those people only count flow from powerheads / their closed loop.

 

[Catpicklesdog]

I only calculate using my powerheads, never any of my other pumps. I'm always one to err on the side of caution:grinyes:

I currently have 5 x 1200gph = 6000 in a 182 gal tank and I could still do with a bit more!!!

 

[apelaston]

reading this i know i need to go buy a few more Powerheads.

And is it better to get a few high flow powerheads or several lower rated ones?

 

[darthgoby]

Thanks for all of the replies. I'm getting a couple more powerheads just to be on the safe side.

In response to the poster who asked if it was better to have 1 large or several smaller, I would think that having more powerheads would be better. That way you can more easily direct the flow to make sure you don't have any dead spots.

 

[Fishieness]

more small ones are usually better. However, it is also really good to have some high flow ones with a wider stream than a few smaller ones. The vortechs or tunzes and even the maxi-mods, hydors, and seios that produce a large wide currect is much better than a straight shot.
As far as not calculating the return pump: that depends ENTIRELY on the system. WIth most smaller tanks, the return seems to be large compared tot he display tank size. mine for instance prodiveds a 20X turnover rate and most give about 10. But if you have a large tank and a small sump, it may not be too much. It just doesnt make any sense to not calculate it...