Quick flow calculation question

[BamaCoastPyrat]

When calculating flow for a sump I hear all kinds of numbers that you should shoot for. I've heard everything from 0.75x per hour to 20x per hour. I'm not hear to debate the optimal number, but is that x number calculated off of display tank volume or total system volume?

 

[TheBear78]

As far as I'm concerned it means system volume as it decides how often all of the water sees the whole filtration system, give or take.
One thing you might consider when deciding on the turnover rate (that your pump is capable of) is how the return flow is used. Are you planning to run reactors and/or a UV off of the same pump? Do you need the return nozzle(s) to add directed flow versus using solely wavemakers?

 

[BeanAnimal]

When calculating flow for a sump I hear all kinds of numbers that you should shoot for. I've heard everything from 0.75x per hour to 20x per hour. I'm not hear to debate the optimal number, but is that x number calculated off of display tank volume or total system volume?

Most suggestions are based on total system volume. In the past, high flow systems helped to generate water movement in the display tank. That made way to closed loops, in-tank devices like wave pumps and gyre pumps.

As mentioned above, your equipment choice in the sump will dictate part of the need, as will your budget (both initial equipment cost and recurring electrical and maintenance costs).

Time to make choices.

Decide WHAT you want in your sump.
Decide what size the sump needs to be.
Decide how you are going to generate water flow in your display.
Decide what type of overflow you are going to use.

Choose your return pump on the answers that those choices dictate.

 

[BamaCoastPyrat]

@TheBear78 @BeanAnimal

I am planning out an upgrade to a 75g. The sump will be 34g with a 29g external refugium. With the planned water heights in the refugium and the sump, I should see 125 gallons in the system minus displacement from sand and live rock. When I set the system up, I am going to measure exactly how much water is in the system.

I will have dual return AC pumps totalling 600-650 gph with head pressure loss factored in and the variable being friction loss. That will put me at about 5x flow on total water volume. I do not plan on using nozzles, but rather just PVC coming from the two return bulkheads.

The overflow is a Fiji cube 1200 which should be more than enough even if I upgrade my smaller pump and have a partial clog in the overflow.

Flow in the display will be maintained by a series of Sicce nano 1000's and 2000's. Using more, smaller powerheads will hopefully keep from blasting small fish while preventing dead spots.

In the sump, I will have a two 200 micron filter socks, and a reef octopus classic 150 int protein skimmer. I do not plan in using reactors or UV sterilizers in this build but I have left room for a reefmat 1200 if I decide I want to go that route in the future.