Return Flow vs. Powerhead Flow?????

[saltygram]

I would like some input from the R2R brain trust on the subject of flow.

I have a 230 gallon system that went live August 1st. After cycling we began adding fish and corals slowly. In general I think we have adequate flow for coral life in the tank, but I'm not happy with some corners of the tank where I can see some stuff settling to the bottom. Here is my current equipment:

Return pumps - I have 2 Sicce SDC 6.0 pumps that are rated (530-1450 GPH). You can see in the photos how I have them running together for redundancy. Each pump is plugged into a different Apex power bar and each power bar is on a different gfci circuit. (I lost a tank in the past when a gfci tripped while on vacation so I wanted redundancy this time.) According to Sicce with my 4.5' head the pumps should put out 800 GPH. With both pumps running through my plumbing configuration I'm getting 570 GPH total, so about 2.5x turn over per hour. (I would have expected a larger output from 2 pumps...)

Power Heads - I'm currently running 2 MP40 power heads on each end of the tank at about 75% output.

Livestock Load - Here is my current fish load in the system:

Sailfin Tang
Purple Tang
Aiptasia Eating Filefish
Blue Chromas (5)
Clarkie Clowns (2)
Cleanup Crew - Snails, Emerald Crabs (8), Blue Tuxedo Urchin

Filtration - The system is a Waterbox Reef LX 290.6 with 2 - 7" filter socks. Also running a Reef Octopus INT150 skimmer. My water parameters are very good and stable. Here were my last measurements from this week:

Nitrates - 0.00
Phosphates - .01
Alkalinity - 7.8
PH - 8.1
Calcium - 395
Magnesium - 1280

So based on these numbers it appears to me that I am achieving enough flow through the tank for proper filtration, although I wish I had more turn over.

My Question:
Do corals benefit from increased tank turnover through return pumps, or do they just need movement of the water in the tank in order to extract nutrition?

Otherwards should I put in larger pumps to achieve increased tank water movement to eliminate the dead spots and keep detritus suspended, or should I add additional power heads to churn the water more?

I think I can achieve my goal either way, but if one way benefits my corals more I'd rather go that direction.

 

[Randy Holmes-Farley]

IMO, return pump flow can be quite low without any concern. Nothing happening in a sump needs rapid turnover. The oft-quoted turnover numbers come from the days when they also supplied the in tank flow. Once per hour is likely plenty if in- tank flow is good.

 

[Mr. Mojo Rising]

IMO the corals only need enough flow to clean themselves and feed themselves.
IMO good flow is more important to the overall health of the tank as you mention. Eliminating dead flow spots while not bothering the corals is always my main goal, I push as much water movement as possible until sand starts shifting and corals receding.

 

[rtparty]

Return pump flow is irrelevant in this context. It’s simply there to bring water to and from the filtration/heating.

 

[dwest]

I agree with the above recommendations.

Aside from your question, are those check valves on the discharge side of your pumps? When 2 pumps are connected, if one pump fails, the second pump will flow back to the first and you’ll have a flow loop through your sump. This won’t happen if there are check valves AND the check valves work. Sometimes they don’t work though.

I personally would have the pumps run with separate return lines to the tank.

 

[mcarroll]

I have 2 Sicce SDC 6.0 pumps that are rated (530-1450 GPH).[...]

What size is that plumbing?

According to Sicce with my 4.5' head the pumps should put out 800 GPH. With both pumps running through my plumbing configuration I'm getting 570 GPH total, so about 2.5x turn over per hour. (I would have expected a larger output from 2 pumps...)

If you measured actual flow at 570 GPH, that's fine for turnover, but you definitely oversized your pumps. A pair of 3.0's would deliver this flow for you.

*IF* you needed the added flow (which your system doesn't) then you'd have to upsize your plumbing more than likely, especially through the Wye where it might benefit from being slightly oversized.

IMO I would trade in your pumps for the 3.0's for the double win – get some upfront cost back AND save power every day you use them. (A smaller pump will use less watts to move the same GPH.)

 

[saltygram]

I agree with the above recommendations.

Aside from your question, are those check valves on the discharge side of your pumps? When 2 pumps are connected, if one pump fails, the second pump will flow back to the first and you’ll have a flow loop through your sump. This won’t happen if there are check valves AND the check valves work. Sometimes they don’t work though.

I personally would have the pumps run with separate return lines to the tank.

Yes, those are check valves to avoid the issue you mention of back flow.

I wish I had 2 return lines, but this system didn't come with that.

 

[saltygram]

What size is that plumbing?



If you measured actual flow at 570 GPH, that's fine for turnover, but you definitely oversized your pumps. A pair of 3.0's would deliver this flow for you.

*IF* you needed the added flow (which your system doesn't) then you'd have to upsize your plumbing more than likely, especially through the Wye where it might benefit from being slightly oversized.

IMO I would trade in your pumps for the 3.0's for the double win – get some upfront cost back AND save power every day you use them. (A smaller pump will use less watts to move the same GPH.)

Pump ReturnDN25 (ID: 25mm OD: 32mm)

I'm stuck with what came with the configuration. The flow chart above doesn't take into account all of the plumbing configuration. I just don't see a way to streamline my setup and keep the redundancy.