How slow is too slow through sump?
- Thread starter EllisJuan
- Start date
Octobot
New member
There are a thousand different ways to do any one thing in this hobby. Sometimes bad practices lead to great results, sometimes good practices lead to bad results. I'm not saying you will have a bad reef tank by running a huge skimmer at half capacity.
What I will say though is that "experienced" EDIT!
What I will say though is that "experienced" EDIT!
Last edited by a moderator:
ReefPharmer
Active member
The person who looks like a ***** is you. You are incorrect in thinking that because it makes sense to you, it must make sense to everyone else, otherwise they are "ignorant". What you fail to understand is that just because the skimmer MAY process and pull out more organics in your theory by somehow magically matchingthe flows of return/skimmer pump, you dont take into account the fact that the stated rate for the skimmer pump is for water movement, not air/water mixing with a pinwheel. How do you figure what that cuts the flow to especially when some skimmers sit deeper than others? My skimmer pump is rated at 700gph... to match that I would have to run the return at 1000 gallons per hour or more to account for head loss... thats quite a bit of movement in a 16 gallon sump.
By the way, I would look to people who have had success in this hobby instead of coming in here and throwing insults with your 55 posts. If it wasnt for others in this community, maybe you'd be boiling your liverock .... just something to think about
Last edited by a moderator:
scottwhitson
New member
+1 you are the one that is sounding ignorant. There is no way that a skimmer removes all organics in that single pass so matching flow rates is not necessarily efficient if you are pushing 700 GPH through the sump if that's what your skimmer is rated at you will need a larger pump than what is necessary meaning you are loosing any efficiency with a larger than necessary pump.
scottwhitson
New member
If this were the case I would have witnessed it first hand with the tank that I am currently building. I have a 600 that I was cooking rock in with phosphates in the 1.5 ppm range. I only run about 1000 GPH flow rate through then sump a all my test results-phosphates, nitrates, ammonia, nitrites were IDENTICAL from display tank to sump.
watsonj
10 & Over Club
I have found 3 x total system volume per hour volume works great with a skimmer that runs at the same flow rate as the return pump, and I don't use the return pump flow as a consideration for tank flow which should be high 10x ext and provided by power heads depending on what you are keeping in the tank.
jimmyj7090
aka John K
On this whole skimmer pump vs return flow rate thing, one detail to consder;
Why are there many "recirculating" skimmers on the market? Food for thought......
Why are there many "recirculating" skimmers on the market? Food for thought......
sc50964
New member
There are enough head loss calculator on the internet to figure out just what your return pump is doing. According to LiveAquaria, the recommended flow rate is 4 times the water volume per hour. Considering that and the amount of head loss I have on the 6' drop between the overflow of my 5' long 180g and the sump, I need a return pump that produces over 2000GPH. My skimmer pump produces 500GPH. If Octobot is correct, then I'm doing something that's seriously wrong. I know I haven't mentioned or considered the contribution of water turn over rate from the in-tank power heads, but the difference is just too much. I test my water on a weekly basis and everything is fine. Fish are thriving and skimmer is pulling out lots of waste. This hobby "can" be an exact science if you want it to be, but why? That seems to take the fun out of it. Trial and error, and experience should all count. Judging or attacking someone based on the number of messages posted or whether if his or her opinion being the same as yours is not right in my mind.
Octobot
New member
I didn't "attack" him for the number of posts he has. I responded to his own comment about not wasting his time talking to someone else. That is pretty arrogant imo.
It is also rather annoying to have someone miss an obvious point such as in the comment "it is actually counter to the argument of matching flow" (it isn't counter ... To say so would mean you believe the sumps higher flow rate is impacting the internal flow rate of the skimmer ... When it very clearly doesn't) while in the same breathe complaining of the lack of cogency. How obnoxious.
Anyway
Another way it seems words were put in my mouth: I never said in all cases you would ever see a difference in your tank depending on sump & skimmer flow rate. In fact, I did point out this would interoperate with the concentration of organics and their rate of production within a tank. Any single experience someone has with two pumps doesn't 'prove' anything one way or the other without taking other factors into consideration as well. A skimmer with a large pump on it capable of skimming lots of water while being fed a smaller rate of water from a return, as many of us do, may be just fine on a given system in the same way that having a slightly smaller skimmer would be just fine. Just because you aren't feeding the skimmer with 100% dirtier DT water doesn't necessarily mean your tank direly needs that to happen in order to remove organics efficiently. Efficiency is removing those organics at the rate which they are being introduced, which varies greatly tank to tank and isn't based solely on the size of the tank a skimmer is rated for.
And this is more of an aside I suppose, but to the responder making a point to prefer trial and error over 'exact science' ... You're not alone in that mindset, but I'll never understand why. Far too many animals die in this hobby for that very reason and it seems generally counter-productive to prefer trial & error in situations where you have the option to get it right the first time.
It is also rather annoying to have someone miss an obvious point such as in the comment "it is actually counter to the argument of matching flow" (it isn't counter ... To say so would mean you believe the sumps higher flow rate is impacting the internal flow rate of the skimmer ... When it very clearly doesn't) while in the same breathe complaining of the lack of cogency. How obnoxious.
Anyway
Another way it seems words were put in my mouth: I never said in all cases you would ever see a difference in your tank depending on sump & skimmer flow rate. In fact, I did point out this would interoperate with the concentration of organics and their rate of production within a tank. Any single experience someone has with two pumps doesn't 'prove' anything one way or the other without taking other factors into consideration as well. A skimmer with a large pump on it capable of skimming lots of water while being fed a smaller rate of water from a return, as many of us do, may be just fine on a given system in the same way that having a slightly smaller skimmer would be just fine. Just because you aren't feeding the skimmer with 100% dirtier DT water doesn't necessarily mean your tank direly needs that to happen in order to remove organics efficiently. Efficiency is removing those organics at the rate which they are being introduced, which varies greatly tank to tank and isn't based solely on the size of the tank a skimmer is rated for.
And this is more of an aside I suppose, but to the responder making a point to prefer trial and error over 'exact science' ... You're not alone in that mindset, but I'll never understand why. Far too many animals die in this hobby for that very reason and it seems generally counter-productive to prefer trial & error in situations where you have the option to get it right the first time.
sc50964
New member
There is no "get it right the first time", not even sea world can claim that. Raising or keeping an animal isn't an exact science coz no two things are exactly alike. All you can ask is for the care taker to do the due diligence to get the basics right, and modify it as the livestock matures. That's the trial and error that I was referring to.
Go back and actually read what I wrote as I think you are taking umbrage at a perceived slight that was not actually written as such. I did not write anything along the lines of 'not wasting time talking to someone else' just that I've been in this hobby long enough to know that there are many ways to skin a cat, as the old saying goes, and 'I have no great interest in trying to dissuade anyone from doing what they think is best'. When you've kept as many reef tanks as I have you realize that many of the things people propose as gospel prove to be somewhat less so.
But enough on this topic ... on to more important things like whether 'live' sand is the biggest waste of money in the history of human civilizations ....
I read the discussion with interest. I have a 400 gallon display with a sump in basement with about 25 feet of head loss. Obviously flow through had bothered me a lot. Right now I getting 1x flow through sump and I have bought an iwaki to potentially get 3x flow through the sump but am still not sure if that would be any better.
Reading above discussion what I concur is that skimmer will remove dissolve organics at y mg/liter/min from sump water creating a differential with display tank of x-y mg/min if display has x mg/l of dissolved organics. If circulation can keep up with difference by providing x-y mg/min then the net difference will always be zero.
That threshold might not be too high but I don't know the answer. Like many things in this hobby that saturation point might not be too much and once achieved going above will not make much difference. The rate of organic removal is likely not same for two 700 gph skimmers. Or for the same skimmer in two different tanks.
Besides efficient skimming there are other reasons for looking at high or low flow through sump. I like the heater argument and I have never bothered to check my display temp and I think I should. I have leaned towards slower flow due to a belief in benthic organisms role in filtering in sump and Refugium. Although I have fuge as separate tank from sump fed by a separate pump, I still plan to allow my sump sections to develop into a benthic bed. There might be other considerations like phosphate reductions, use of deep sand beds and macro algae growth. Etc.
Reading above discussion what I concur is that skimmer will remove dissolve organics at y mg/liter/min from sump water creating a differential with display tank of x-y mg/min if display has x mg/l of dissolved organics. If circulation can keep up with difference by providing x-y mg/min then the net difference will always be zero.
That threshold might not be too high but I don't know the answer. Like many things in this hobby that saturation point might not be too much and once achieved going above will not make much difference. The rate of organic removal is likely not same for two 700 gph skimmers. Or for the same skimmer in two different tanks.
Besides efficient skimming there are other reasons for looking at high or low flow through sump. I like the heater argument and I have never bothered to check my display temp and I think I should. I have leaned towards slower flow due to a belief in benthic organisms role in filtering in sump and Refugium. Although I have fuge as separate tank from sump fed by a separate pump, I still plan to allow my sump sections to develop into a benthic bed. There might be other considerations like phosphate reductions, use of deep sand beds and macro algae growth. Etc.
I'll leave the skimmer flow question alone, I think I've made my perspective clear on that one. The heating question is an important one as clearly if flow is too slow, temperature might drop in the display relative to the sump. Also, if flow is too slow, you may not get adequate surface skimming. Frankly, there is nothing really wrong with high flow through the sump (as long as you aren't pushing your drain pipes too much), it has just always struck me as unnecessary and potentially a waste of electricity - but it's not going to affect the success of the tank.
Octobot
New member
That is a great point. Unfortunately chaotic mixing in fluid dynamics is a supremely difficult thing even for software to compute - so I doubt either of us will come to the answer ourselves!
It would be possible with sensitive enough instruments to determine the average difference, if any, of particular organics between the sump and display. Our little API reagents wouldn't exactly cut it though.
okay....so here's a question I didn't notice being addressed. So what about stuff in the water column. The faster the flow through the sump, the more it will be sucked out the overflow and not settle in the DT right? Wouldn't this move more "junk" to the skimmer and therefore out of the system?
My suspicion is that its not significant as long as one employs in tank power-heads to maintain proper flow. Prior to effective power-heads, I used to subscribe to the 'massive flow through sump' school of thought, and my tanks built up significant detritus behind the rockwork. Now, with pumps like vortech, tunze, etc., and low flow through the sump, I actually have far less detritus build up.
Reefer54
New member
im ready to be beat up.
i personally run a reef octopus waterblaster 10000 as my return with 12 or 13 ft of head loss, i forget, which gives me roughly 15x turnover through my sump. skimmerless.
Here is my thinking and take it with a grain of salt.
with that much turnover, i do get some flow in my tank from my return, but not solely. i use one other pump and a powerhead to achieve a DT volume turnover rate of about 28x. I personally believe that if we are going to spend as much money on return pumps as we do, we may as well get more than we need and dial down, plus use it as an added amount of flow while not solely depending on it. powerheads are way to specialised to not use them....even if i dont want to see them.
that being said, i have no emergency drain, but a 1in. and 3\4in drain which allows me to have the flow draining to keep up with the return.....why....water passing over the most surface area possible. my sump is stocked to the gills with LR and LS and two algae scrubbers, one up flow, one down....and params are almost too low....i may pull the half dose of biopellets here soon. undetectable nitrate is frustrating me, and i feed heavy to a moderate bioload.
When it comes to skimmers, i have heard the 30% suggestion as posted above, and i cant say i disagree. I rely on LR and LS to take care of water quality and i help remove DOC (though i could probably do a better job).
But as posted above, what works for me may not for you. my sump is not a pretty display sump, but the DT stays nice and clean. I never agreed that the more time water sits in the sump the cleaner it will get....i think the more surface area water passes over, the cleaner it will get, and when i used skimmers, i never really felt like i was getting a ton more stuff than i do by hand out of my water. plus, i know i am not pulling pods and detritivores out. I should mention i have a semi cryptic area also which i never clean, perhaps
mostly a good read. there are many ways to scale a fish i guess.
i personally run a reef octopus waterblaster 10000 as my return with 12 or 13 ft of head loss, i forget, which gives me roughly 15x turnover through my sump. skimmerless.
Here is my thinking and take it with a grain of salt.
with that much turnover, i do get some flow in my tank from my return, but not solely. i use one other pump and a powerhead to achieve a DT volume turnover rate of about 28x. I personally believe that if we are going to spend as much money on return pumps as we do, we may as well get more than we need and dial down, plus use it as an added amount of flow while not solely depending on it. powerheads are way to specialised to not use them....even if i dont want to see them.
that being said, i have no emergency drain, but a 1in. and 3\4in drain which allows me to have the flow draining to keep up with the return.....why....water passing over the most surface area possible. my sump is stocked to the gills with LR and LS and two algae scrubbers, one up flow, one down....and params are almost too low....i may pull the half dose of biopellets here soon. undetectable nitrate is frustrating me, and i feed heavy to a moderate bioload.
When it comes to skimmers, i have heard the 30% suggestion as posted above, and i cant say i disagree. I rely on LR and LS to take care of water quality and i help remove DOC (though i could probably do a better job).
But as posted above, what works for me may not for you. my sump is not a pretty display sump, but the DT stays nice and clean. I never agreed that the more time water sits in the sump the cleaner it will get....i think the more surface area water passes over, the cleaner it will get, and when i used skimmers, i never really felt like i was getting a ton more stuff than i do by hand out of my water. plus, i know i am not pulling pods and detritivores out. I should mention i have a semi cryptic area also which i never clean, perhaps
mostly a good read. there are many ways to scale a fish i guess.
M_Jaco
New member
I've always run relatively slow flow through all my sumps. I generally house a large amount of live rock rubble in my sumps, and it offers a great place for detritus to settle out as well as a lot of surface area for the water to contact. The more time the water contacts all this rock, the better it can filter it.
In terms of skimmers and flow, IMO it makes way more sense to have the skimmer pump running significantly higher than the flow through the sump. From an engineering standpoint this creates more of a "completely mixed flow reactor" AKA all the water in a given section is mixed homogeneously. One can assume this is being done by the skimmer circulating water through the section. The slower the flow through the section in your sump, the more time the water has to be "completely mixed." The theory of a "completely mixed flow reactor" is the assumption that one makes when designing water filtration systems, such as those in wastewater treatment plants.
Now this is different if your skimmer is gravity fed by your overflow with a recirculation pump as the produced of bubbles/turbulence in the body. But even still, just because 100% of the drain water is flowing through the skimmer before returning to the tank, it doesn't mean 100% of the dissolved organic solids are being removed. Personally I'll take the low turnover/higher flow skimmer pump combo any day.
These are all just my thoughts and practices on the matter. I have a little experience with wastewater treatment design/theory, and in my head the sump in my tank runs on the same basic premises.
In terms of skimmers and flow, IMO it makes way more sense to have the skimmer pump running significantly higher than the flow through the sump. From an engineering standpoint this creates more of a "completely mixed flow reactor" AKA all the water in a given section is mixed homogeneously. One can assume this is being done by the skimmer circulating water through the section. The slower the flow through the section in your sump, the more time the water has to be "completely mixed." The theory of a "completely mixed flow reactor" is the assumption that one makes when designing water filtration systems, such as those in wastewater treatment plants.
Now this is different if your skimmer is gravity fed by your overflow with a recirculation pump as the produced of bubbles/turbulence in the body. But even still, just because 100% of the drain water is flowing through the skimmer before returning to the tank, it doesn't mean 100% of the dissolved organic solids are being removed. Personally I'll take the low turnover/higher flow skimmer pump combo any day.
These are all just my thoughts and practices on the matter. I have a little experience with wastewater treatment design/theory, and in my head the sump in my tank runs on the same basic premises.
