How times per hour do you turn your tank over?

[flowerseller]

From someone who has a sump,

My 220 display gets about 2-3 x per hour and I have several water movers inside it.

My 90 and 60 also get about the same, all from the same pump from the sump.

My down draft skimmer gets about 800 - 900gph also from the same pump as the tanks.

[s2nhle]

I have mine turned over around 3x.  So my skimmer can remove the waste more efficient.

[Origami]

Removing off-topic, unwarranted aggressive post. Get back on topic, please.

 

OP, to your question: I can't tell you honestly what the turnover rate is in my sump. If I had to guess, it's probably 3x or so. But I could be way off.

 

Looking at it from an analytical point of view, you probably want to start by looking at the turnover rate and contact time in the skimmer and then try to ensure that the flow through the sump is sufficient to keep the skimmer fed with enough water that it's doing it's job effectively. In a non-sump system, where all the water is fed directly into the skimmer and returned back directly to the tank, you're guaranteed that all the water entering the skimmer is 100% un-skimmed tank water. In the case of the sump, the output of the skimmer is dumping "clean" water right back into the sump where it mixes and dilutes dirty tank water. That diluted water then goes back into the skimmer body possibly making it less efficient from a time-use perspective. I'm not sure if there's any credibility to this... just trying to put a little analytical spin on it.

 

Someplace in the archives here, Ctenophore (Justin from Avast) posted something about how to size your skimmer based on contact time with the water.... It seems that sump turnover rate might be tied to that, ideally.

[Reefer_Madness]

I think I got hung up on the tank size vs how many times I should turn it over.  I'm going from a 60g to a 120g and started thinking about twice as much water going through my sump.  Twice as much water through my sump seemed excessive.  Too much flow. 

[Reefer_Madness]

I started with 2x turnover in my tank and noticed a swing in temperature.  It makes sense.  I keep my heaters in the return compartment of my sump.  If I am not pumping the warmer water up to the tank, then it can't keep up with heat loss.  I am going to bump my turnover up until my temperature fluctuations level out.  I don't want to put my heaters in my tank. 

[Origami]

I started with 2x turnover in my tank and noticed a swing in temperature.  It makes sense.  I keep my heaters in the return compartment of my sump.  If I am not pumping the warmer water up to the tank, then it can't keep up with heat loss.  I am going to bump my turnover up until my temperature fluctuations level out.  I don't want to put my heaters in my tank. 

Great observation. I'm somewhat surprised that a 2x/hour turnover has that effect but the proof is in the practice. Just curious: What would you say is the percentage of your overall system water volume is in your sump?

[Reefer_Madness]

Sump holds like 30g.  Tank is a 120g.  The 2x/hour turnover is just a guess really. It could actually be less then that.  I'm just eyeballing and guessing.  The swings are not huge, but they are more than I had at about .6 degrees.  My other tanks were around .2. 

 

Another interesting thing is that the tank is, on average about .3 degrees less than what I have the Apex shutoff set at.  That is probably because of my redundancy.  I have the heaters themselves set to turn off at 8.1, so my sump compartment is probably at 8.1 and the individual heaters are turning themselves off.  You think?  I could probably keep the flow the same and turn the individual heaters up to 8.3 or so, but that makes me a little nervous and cancels out my redundancy plan. 

Edited April 7, 2016 by Reefer_Madness

[Jon Lazar]

Can you collect some actual data on your return flow vs. the DT/sump temperature differential?  Maybe something simple like how long it takes your return to fill a 5 gallon bucket.  That would help the community form a more informed position about low-flow sump systems.

Edited April 7, 2016 by Jon Lazar

[treesprite]

Right now, for my 75g, I have separated sump and refugium with two different pumps. I havent done the math, but sump to tank is probably between 1200 - 1400, and regugium to tank between 100 - 150.

 

The sump overflows to fuge at whatever rate the fuge flows to tank, which allows me to use the fuge pump to fine tune the water level in my overflow without having to adjust the main pump or overflow pipe valves. Im not concerned about the high flow rate related to skimmer, because of the way I have my sump made and where the skimmer output is in it. But if you only have one pump and a typical sump arrangement, you might want to use a pump that isn't super high flow.