The SUMP SLOW DOWN: The benefits of slowing down the water?

[Doglips56]

With plenty of water movement and lots of live rock in the DT there is no need to turn your sump into a spin drier. One of my most successful tanks had a turnover of once every 3 hours through the sump. Lots of live rock, water movement. Skimmer was also in the sump along with biological media to help keep nitrates in check mainly. This is me about 30 us years ago with said tank.

We had a much smaller than that tank 30 years ago, didn’t even know the sump method existed back then. We thought our undergracel filter was top of the line lol. Nice throwback pic!!!

 

[atoll]

We had a much smaller than that tank 30 years ago, didn’t even know the sump method existed back then. We thought our undergracel filter was top of the line lol. Nice throwback pic!!!

Same here. First tank I had a UG filter with an air pump that would vibrate so much your fillings would fall out. Later I converted it to a reverse flow UG.

 

[mfinn]

IMO the flow through the sump isn't going to change the amount of water the skimmer is going to process ( unless you have all of the water going into the skimmer first). It can only process the amount of water the feed pump pushes into it.
I do think maybe a slower flow through the refugium allows for more contact time with the macro. I have seen in my systems that water movement in the refugium benefits cheato. I add a powerhead in it to create that movement rather than trying to create more flow from the return pump.
So my systems, I use a moderate flow. Usually in the 5x to 6x the tank volume.
Part of that reasoning is also tied to noise from water moving to and from the sump and a little in part to power usage. ( although with todays dc pumps, that part is pretty much void. But old habits are hard to give up.

 

[radiata]

Seems to me that the higher the flow, the more uniform your tank water will be. I can't see how having concentrated pockets of any constituent of the tank water would be a good thing.

 

[Whasmack]

I have not really seen a benefit to running a high turnover sump- I've ran them fast & I've ran them slow.
Typically, on smaller systems (lets say around 40g) I run 4x-8x turnover & on larger systems (180g, 300g) I'll run it closer to 2x-4x.

 

[LegendaryCG]

A slow sump is a settling tank.

 

[ams_reef]

I have 15x turnover on my system through my return pump (Eheim 1260 on a RedSea Reefer 170). I don’t see any difference in skimmer performance when the return rate was slower.

I could be wrong but as far as I understand the level of DOC’s in the display is the same as the sump (barring any exceptionally slow flow rates) so altering the return pumps flow wouldn’t matter. The more important factor would be contact time via the gate valve adjustment. Please correct me if I’m wrong.

I personally like my high flow sump. The oxygen levels are probably higher given that I direct the return flow at the water surface. I have very little variance in temperature (I do have an inkbird controller) and the overflow/sump system is very quiet. The only downside I can see especially on small systems like mine is the tunze ATO is probably a little more sensitive. Keeping salinity levels hasn’t been an issue at all though.

 

[Greybeard]

3x tank per hour capacity would be my minimum. Why? Less than that, and I start noticing temperature variances between the sump and the tank. Want to keep it all homogeneous.

I tried Triton at one time... including the 10x recommended rate. Didn't work for me. Skimmer wasn't very efficient, nutrient levels higher than I'm willing to live with. Just don't think Triton is a good idea for a new tank, which mine was, at that time. I know it works well for some folks, just not my cup of tea. (My cup of tea is most often a dram of scotch, so...)

I'm doing the Zeovit thing these days, with much better results. Flow rate probably 6x tank volume per hour. Not running a fuge, so don't need reduced flow for that... Carbon and Marinepure blocks are in low flow areas of the sump, no need to force high turnover rates through them. Skimmer seems to be operating as efficiently as ever. I'm changing sox every other day... seems pretty stable at this point. No need to change anything.

 

[Bruce Burnett]

So how fast do you want surface of tank skimmed. How much flow through sump is required. I do not believe it will make a difference with the skimmer unless you get it so slow that it can process more volume than it is getting. Refugium depending on setup may need a lower flow. I have always looked at a balance of noise, tank size, head pressure. I shoot for 15 times tank volume at 8-10 ft head pressure and then it is what ever it is. I figure I get close to 10x final flow. But I have been as low as 3-4 times.

 

[Admann]

I voted "not sure". I'm thinking that in separation and treating vessels in the oil/gas production field you want to increase "residence time" in those vessels for better separation of the fluids and commingling of treating chemicals before moving on to the next vessel or pipeline in the process. The whole reason is to achieve the most efficient use of your available capacity, vessel function and chemical treatment (reef aquaria, biological processes) until it goes upside down or terribly inefficient. in short you start out low flow and increase until you reach the optimum conditions or diminishing returns.

Think of the inlet or sock filter section as your surge vessel, refugium section as a rough seperator, skimmer section for polishing the water and the return.

Hope that makes sense

 

[Peach02]

I am no expert however I think depending on what filters you are using it will. Skimmers, refugiums and reactors would all benefit from having more time to work with water however filter socks / rollers won't.
I think between 4-6x turnover through the sump is good for most systems but if you have UV or something a dedicated closed loop or something may help.

 

[Anchor]

Based on what I have read so far, sump flow is a tunable parameter just like anything else. Find what keeps your NO3/PO4 in acceptable ranges based on the combination of skimmer tuning, refugium flow and sock usage/change out - plus flow thru. In fact, to me, sump flow thru might be the closest to set it and forget it for filtering parameters that I have. I don't feel it wil have as much effect on filter efficiencies as other things could have.

You have to look at this as a system and not just a single parameter that can do a job on its own. All of your filter/sump tools need tuning. So, sump flow thru is a tunable parameter based in the efficiencies of the rest of your filter tools.

As to being too slow of flow making your sump a detritus dump. I find that it is easier to locate and remove detritus from the sump than from the DT. This seems especially true if you have some form of sand/gravel in the DT. Blowing detritus out from under your rockwork to gather it may be very difficult with sand in place.in fact getting a lot of your detritus build up may prove impossible with sand in place. Regular sand stirring and allowing it to settle into the sump might be an easier way to get it out of your system than just gravel vacuuming -- Sock or no sock.

 

[Anchor]

I figure I should add on a couple of things..

Flow through might depend on if you have a variable DC pump or have to go out and buy several different sized AC pumps -- If you want to tune it.. thus my set it and forget it.. go tune something else.

This is all ONE filter not several filters.

Tune one thing at a time, not all at once.. Otherwise you may knot know what thing you adjusted actually had the effect -- positive or negative

 

[Chris Shelton]

I'm totally new to saltwater of about 15 months. We have a 150G DT with a DIY 30G sump. Spent the first year FOWLR as we were expecting a move. Moved In Sept. so after tank move. its about 6 months old. Found a steal in the DT and it was ran fresh water so only had 1 side overflow Durso plumbed in 1" and at the time 600GPH was just understood as not acceptable so I added a 16" Synergy overflow with Bean Animal in the back center plumbed in 1.5" so I have a 1" (with gate valve) draining into the skimmer area as well as an 1.5" (again with gate valve) beside in the skimmer area. I sometimes run socks on those drains and notice less floating particals in the DT but the skimmer seems to work better without the socks. The center chamber is Chaeto with a H380 ran 12 hours opposite the DT and it seems to grow better without the socks even though the RO cup almost looks like mud. Third return section has twin Simplicity 1600 DC pumps currently running at 50%. I have one BRS 300W heater in the side overflow and another BRS 300W in the return section. Both controlled through the BRS controller and Apex. I just did water tests and had 78.2 in the DT and 78.2 in the sump with Apex probe reading 78.4 Temp stays within 1.3 degrees but that may be the way I'm running the system. That flow rate (which I am unsure of x's turnover cause I haven't figured it) seems to keep consistent temp. I voted yes slower is better simply because I previously had a 10,000 Koi pond and the only filtration I had on it was a leaf screen (kinda like a pool to catch the big stuff) then a filter pad to catch floating stuff then about a 1000 gallon 2' deep "fuge" we will say called a bog in frershwater life and it was 5.5' deep and you could see bottom year round. Kinda the same thought process. let the plants process out all they can...Just my .02 cents

 

[Mastiffsrule]

The water being pulled into your skimmer is dependent on the pump that feeds the skimmer. The flow rate around it wouldnt matter.

Agreed, that there is the perfect answer.

I actually (and I’m no scientist) think higher flow would reduce skimmer performance. The pump would be fighting to pull in water from the higher current.

At the risk of forum shame, too much emphasis is put on turnover unless utilizing a refuge. This is my opinion, but most of us use sumps for extra volume for stability, hold equipment, and use for dosing and other stuff. All that can be achieved at 3x or 10x turn over. As long as the DT has the flow and surface agitation you should technically be able to take a sump off line and still run the tank with no problems. You may have to put the heater in the tank and do more water changes and manual dosing and testing, but that is a Berlin system and it works. I had a plumbing problem last year and took my sump off line 3 weeks, I actualy think my tank did better.

Just a thought when we talk flow and how important it really is thru the sump.
keep on reef y’all.

 

[oldbob50]

I voted other: I do both. I custom designed my sump with the fuge not inline with the main tank flow. Most of my overflow goes through the sump based on my return pump speed. That flow hits the skimmer, heaters and carbon reactor. Flow throught the reactor is controled by its pump and valve. Flow through my fuge is a separate smaller overflow line with a ball valve for control. The fuge is a pod factory and a place for frags rather than for nutrient export. I have never been able to get macro algae to grow in the fuge, although it is covered with coralline algae.

 

[Phildago]

My hypothesis is that slowing it down in the sump allows all the benefits of the sump to take full effect on the water before its pumped back into the tank. This means that your constantly pumping water back into the tank that is the best possible quality. Whether that be temperature, salinity, alk, ca, etc...

 

[Dan_P]

I voted “no” to slower flow. Here’s why.

The goal to achieve with flow to the sump is to keep the water chemistry the same as the display tank, ensuring that all the devices are treating display tank water. This also means maintaining the oxygen level elevated throughout the system. There is no downside to high flow to the sump except a waste of electricity. Slowing the flow below the level needed to keep the sump water and display tank water identical provides no benefit to water quality.

 

[ca1ore]

I have always targeted around 3x to ensure even heating between the sump and display and proper surface skimming. Go higher than that if you wish, but I see no advantage to it. Hard to see why macros would grow any better in slow versus fast turnover, as long as the flow doesn’t dislodge it. Algal turf scrubbers have no problems extracting nutrients from fast flowing water, don’t see why macros would be any different. Skimmer efficiency is also unaffected by turnover. Pass through skimmers process water quickly, recirculators slowly ... and I’ve not seen any notable performance differences between the two approaches.

 

[Nanorock1970]

Same here. First tank I had a UG filter with an air pump that would vibrate so much your fillings would fall out. Later I converted it to a reverse flow UG.

Oh Yess I remember that was how I set up my attempt at salt water 30 years ago with the reverse flow UG. I forgot about that..It was bleeding edge tech for salt and you had to make pretty much everything because there was not much being mass produced or available in the stores near my house....(lack of internet and all). Eh, I made it 4 months with my 3 fish back then. Didn't try again until last year. No sump, running a canister and all is good a year and a half now.
So to slow the sump,,,,you can only increase contact time with a given flow through the sump. Flow is flow. What goes in has to go out. I guess more baffles would give you more contact time in the sump but I am not sure about the benefits.
I think, fast enough to maintain heat/or chiller depending on your location and enough water that the skimmers and fuge have enough effluent to process and keep the DT clean.