Quick question on refugium flow rate

dugthefish · Nov 7, 2018

Considering a diy refugium. Water pumped in from T on main return line, gravity feed back into sump return section.

When people talk about flow rates as 3x,5x, 10x, are they talking about 10x refugium size, or 10x total system volume?

miPapareef · Nov 7, 2018

Those numbers are usually total system or at least DT size based.

Ron Reefman · Nov 7, 2018

miPapareef said:
Those numbers are usually total system or at least DT size based.

I hate to say you are wrong, but I think you are confusing flow in the tank vs flow in the sump. I'd certainly would ask whoever is giving you that information.

IMHO, if somebody told me their refugium flow rate was 5x, my assumption would be that they are talking about 5 times the volume of the refugium, not 5 times the volume of the DT or the entire system ( the DT or entire system volume doesn't really relate to flow rates in the refugium). That is to say, if I have a 100g DT and a 50g refugium and I want a 5x flow rate, here is what I would do. The 50g refugium times 5 is 250gph. Doing 5 times the display tank would be a 500gph or doing the entire system would be 150g times 5 which is 750gph. OK, so now let's say you have a 300g DT with a 50g fuge. Doing just the fuge at 5 times would still be 250gph, which makes sense. But 5 times the 300g DT size would mean 1500gph in the fuge! And the bigger the gap between the size of the fuge and the size of the DT would just make the problem even worse. What about a 1000g DT with a 50g fuge (absurd I agree, but it's just an example of why you want to use the size of the fuge) then 5 times the DT volume would be 5000gph through a 50g fuge... now that is absurd. But 5 times the volume of the fuge is still just 250gph, which makes sense.

theMeat · Nov 7, 2018

When people talk turnover rate, 3x, 5x, 10x etc, they are talking display tank size. Refugium, depending on what macro you have, also has a recommended flow rate. Cheato likes more, caulerpra less

Instead of a tee with valves to control flow to display and fuge, IMO better off with separate pumps so you have a better idea of gph you’re delivering

Ron Reefman · Nov 7, 2018

Just to be perfectly clear, I have 4 different turnover rates.
1) the entire system (fairly meaningless)
2) the DT (very useful for corals)
3) the refugium (useful for whatever you have in there and it varies based on just what that is)
4) the sump (less important but still can be useful, especially if you don't have a refugium)

It's always smart to make sure you know just what any given turnover rate is for. Most reefers are most interested in DT flow.

Subsea · Nov 7, 2018

You should check out BRS TV Investigates. They used refugium volume to express volumes flowed. I looked at five videos on algae filtration as primary nutrient management.

Their is no one absolute flow rate that is best. In my 75G tank, my 30G refugium flow rate is 750GPHr, which assist with display tank circulation. In my 120G 1 year set up, I am running a 40G cryptic refugium with a 150G an hour flow rate. Display tank circulation is 30 volumes per hour. With respect to nutrient management in refugium, light intensity is much more important than flowrate.