I'm new to saltwater and tank is currently 2 weeks into cycle. Just wondering what ideal return pump flow is. I've got the reef octopus 3500 DC currently running only 3/5ths power. With head loss calculated right now it's running at 471 GPH. Is this about right or too much? My skimmer says it pulls 105 GPH so didn't know if I should dial return down or if the higher turnover from DT to sump is more beneficial? Thanks!
Return pump flow
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Most will say to shoot for 10 times turn over in the display. My personal opinion is somewhere in the range of 5-10 times. You didn't indicate what your tank size is, so can't provide a number, but it's pretty easy math. You'll also need to know what your overflow system is rated at as well, simply not to not overshoot what it can handle.
Anyway, shoot for that range on your return. You'll then add internal flow in the tank via circulation pumps/powerheads. That amount of flow is dependent upon your inhabitants.
Hopefully that helps give you an idea.
Anyway, shoot for that range on your return. You'll then add internal flow in the tank via circulation pumps/powerheads. That amount of flow is dependent upon your inhabitants.
Hopefully that helps give you an idea.
Thank you both for taking the time to reply. That definitely helps. And sorry about that, tank size would have definitely helped. Lol. It's a 60 cube with 600 GPH overflow. I've got 2 mp10's inside the tank for water movement.
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Pewmichael
Community Member
Hi,
Basically you want to get all the volume of the tank to pass through your skimmer and filtration as many time per hour as possible. At least 10 is good, more the better.
Work out the water volume of your tank LxWxHx1000=liters ( sorry I'm
Metric). Let's say your tank is 90 liters your return pump should be at least 3500 liters Per hour.
Basically you want to get all the volume of the tank to pass through your skimmer and filtration as many time per hour as possible. At least 10 is good, more the better.
Work out the water volume of your tank LxWxHx1000=liters ( sorry I'm
Metric). Let's say your tank is 90 liters your return pump should be at least 3500 liters Per hour.
DamianOZ
Active Member
I aim for sump flow to equal the skimmer flow though rate.
As it works out, my current tank turns over about 2x per hour
i'm not a fan of higher flow via sumps, its inefficient and harder to deal with (greater head volume, bubble issues, noise issues, plumbing size, more power loss, more heat, ....
As it works out, my current tank turns over about 2x per hour
i'm not a fan of higher flow via sumps, its inefficient and harder to deal with (greater head volume, bubble issues, noise issues, plumbing size, more power loss, more heat, ....
I'm lost in your math there a little. 3500 is almost 40x the 90...
I respectfully disagree. I see your point about the skimmer flow rate but not all the water you pass through the sump passes through the skimmer. So by doing the flowrate of your skimmer you're under-running it theoretically. As for the problems you're mentioning with higher flow rates are not really problems.
1) Head volume / plumbing size: I assume you mean that your volume in the lines will change with the plumbing size change to accommodate a bigger pump and/or higher flow rate. For a sump under the DT in a stand the change will be minimal. Now if you're running to the basement or something equivalent then probably your plumbing will be big anyway.
2) Bubble issues: I don't see that as a problem either. Smart placement of baffles and they're gone.
3) Noise: If you implement a herbie/beananimal then no noise at all on the overflow. On the return, a nice DC pump will eliminate all noise making it perfectly silent.
4) Power loss: I am not sure why that would happen.
5) More heat: If the pump is a DC one that's a non issue either.
There hasn't been a study proving that more/less flow turnover through the sump is more/less efficient so everybody is guestimating using anecdotal evidence and what has worked for other people. The way I approach it is that the relationship of filtration efficiency versus tank turnover through sump/filtration equipment is a proportional one to a point of diminish. I imagine it as a logarithmic function. So the way I approach it is on the higher end of the turnover.
I hope I am not coming across as an argumentative a**
DamianOZ
Active Member
Head volume = The volume of water in the display that is above the water level of when the pump is off. If you double the flow, the level doubles. With a power out, your sump needs to be able to hold this volume.
A return pump, pumps up hill, there is head loss from this hight and plumbing. You simply can not create the same volume of water movement in the display using the return as you can using wave pumps. There for the use of return to create water movement is inefficient.
I disagree with you on the skimmer point. FWIW, I do use a DC return pump, I have run it at 620L/h and turning it down to 300L/h hasn't shown any difference to skimming. The skimmer output was tested at 300L/h during set up.
I do use silent over flows, I actually make them from acrylic, no stand pipes, only 20mm (4/5") wide.
No hassle with disagreeing with me, I enjoy learning of other peoples ideas, sometimes they change my thinking, other times not
Sure, there are ways to deal with every point, other than the power efficiency factor. But what is the benefit of more flow? may be so you have no pumps in the display? I can appreciate that. May be you run some other device in the sump requiring more flow? other than that I can't think of any.
A return pump, pumps up hill, there is head loss from this hight and plumbing. You simply can not create the same volume of water movement in the display using the return as you can using wave pumps. There for the use of return to create water movement is inefficient.
I disagree with you on the skimmer point. FWIW, I do use a DC return pump, I have run it at 620L/h and turning it down to 300L/h hasn't shown any difference to skimming. The skimmer output was tested at 300L/h during set up.
I do use silent over flows, I actually make them from acrylic, no stand pipes, only 20mm (4/5") wide.
No hassle with disagreeing with me, I enjoy learning of other peoples ideas, sometimes they change my thinking, other times not
Sure, there are ways to deal with every point, other than the power efficiency factor. But what is the benefit of more flow? may be so you have no pumps in the display? I can appreciate that. May be you run some other device in the sump requiring more flow? other than that I can't think of any.
I fail to see why that would be the case if your draining system can take the rate the pump is providing. Am I missing something?
The reason for more flow from my perspective is not turbulent flow in the DT. It's mainly efficiency of filtration and oxygenation. The more water moves through the sump (up to a point) means the more of it exposed to the filtration means efficient filtration and more oxygenation. Of course if you turn your sump over 1000 times your display volume it won't be much different than say 50 (other than tearing everything apart). I guess the argument is where is that line drawn, i.e. where the efficiency of the filtration is enough. As I said there is huge debates around on the rule of thumb and if you ask ten people you'll probably get ten different answers simply because everyone has something that works for them and it's hugely anecdotal based on experience. For instance my experience is with a 30 gallon tank. That volume and size allows me to oversize equipment and filtration much easier than say a 300 gallon tank. And if I had that size tank I don't know if I would still like or could afford or would pursue my 30x turnover that I have now.
With that in mind, on the original point you made, for my tank it's not inefficient nor harder to deal with to have this huge turnover. But like I said, on a 300 it would be a whole new ballgame.
No hassle with disagreeing with me, I enjoy learning of other peoples ideas, sometimes they change my thinking, other times not
Same here. Especially on issues like this. Our hobby has changed drastically over the decades and we sure don't know where we will be and what we'll believe in ten years.
DamianOZ
Active Member
If your using a full syphon method, oxygenation is irrelevant.
Sure, if you have media that requires more flow. I don't.
Yes you are missing something.
When you turn the return on, the water level in the display rises, the hight to which it rises is determined by the over flow length. (Plus water viscosity, but not relevant for the argument). You can calculate what the rise in level is going to be, I don't have the formula handy. However, if the water rises 1/2" with a return of 200g/h, it is going to rise close to 1" if you increase the flow to 400g/h
The volume of this water is, this high difference x the tank length x the tank width. This is the volume of water your sump needs to handle if you turn the return pump off. So, double the return flow, double the water...
Sure, make a bigger sump, or design it different, make larger over flow, use larger pipes, use more power running larger pumps.... it all works, if efficiency is you priority, then sump flow greater than that required by the equipment is a waste.
Do the math, check out the power usage for pumps, their flow curve to gain actual flow figures. Work out the most efficient combination for the flow you want, you will find slower turn over much less expensive to run, the pumps run 24/7.
If you think Activated carbon, perigean, turf scrubbers, sand filters, or other media is more efficient with greater than the tank passing it 40 times per day.... you guessing!
I also use UV and a chiller, my return flows via them in series to the tank. Both are most efficient at 300 - 600L/h, so I can use the one DC return pump. If I had higher return flow, I would have to run additional pumps.
20 years ago, Tunze released the first wave pumps, that year saved me $300 per quarter in electricity, I have build 5 displays since, and each I plan power consumption of the pump vs flow for most efficient operation... IMO, this 10x turn over or required minimum is a myth.
Anyway, I think we have bashed it enough.... at least the OP has some food for thought in making their judgments
Sure, if you have media that requires more flow. I don't.
Yes you are missing something.
When you turn the return on, the water level in the display rises, the hight to which it rises is determined by the over flow length. (Plus water viscosity, but not relevant for the argument). You can calculate what the rise in level is going to be, I don't have the formula handy. However, if the water rises 1/2" with a return of 200g/h, it is going to rise close to 1" if you increase the flow to 400g/h
The volume of this water is, this high difference x the tank length x the tank width. This is the volume of water your sump needs to handle if you turn the return pump off. So, double the return flow, double the water...
Sure, make a bigger sump, or design it different, make larger over flow, use larger pipes, use more power running larger pumps.... it all works, if efficiency is you priority, then sump flow greater than that required by the equipment is a waste.
Do the math, check out the power usage for pumps, their flow curve to gain actual flow figures. Work out the most efficient combination for the flow you want, you will find slower turn over much less expensive to run, the pumps run 24/7.
If you think Activated carbon, perigean, turf scrubbers, sand filters, or other media is more efficient with greater than the tank passing it 40 times per day.... you guessing!
I also use UV and a chiller, my return flows via them in series to the tank. Both are most efficient at 300 - 600L/h, so I can use the one DC return pump. If I had higher return flow, I would have to run additional pumps.
20 years ago, Tunze released the first wave pumps, that year saved me $300 per quarter in electricity, I have build 5 displays since, and each I plan power consumption of the pump vs flow for most efficient operation... IMO, this 10x turn over or required minimum is a myth.
Anyway, I think we have bashed it enough.... at least the OP has some food for thought in making their judgments
It's not only the oxygenation from the drain pipe mixing air (durso, stockman, other) but also the fact that the water goes over baffles and through sponges etc. I am sure you can design an experiment to quantify it and see if it's relevant or not but it's beyond the point.
I still fail to see why. If, and I say a big if, your overflow system can handle the pumped rate I am not sure why it would be different. Now, when I say overflow system I mean not only pipping but also overflow slots and in general the whole concoction that overflows water from the display to the sump.
If you do find anything explaining this, or the formula you mentioned, I would be really really interested in checking it out. That would help me clarify this in my head once and for all and I'm sure plenty of other people would find it useful.
All I am saying is that up-sizing your pump (especially when it's DC) one or two sizes might cost you let's say at most 50W. Doing the math and factoring a $0.1/KWh I come up with $3.6/month or $43.2/year. It's up to the individual to consider if it's worth or not.
As I mentioned before, both of us are guessing. I don't have scientific evidence that it's better nor that it's worst or irrelevant. There is definitely a way to get it which is designing an experiment where the only variable would be flow and collecting the data but it's an insignificant matter enough to not be worth it.
I know that Aqueon has done some pretty extensive research on their side with the design of their HOB's factoring in surface area of the filter pads, flow rate, carbon grade and porosity, filter porosity etc which is amazing in of it's own. In their experiments they showed that the efficiency of filtration versus flow rate is like a negative square function with an apex at a certain flow rate. That's where they set their flow rates for their Aqueon series HOB's btw. This showed that actually too much flow harms filtration so does too little. I am not aware of anything showing this relationship in terms of sump turnover and what we are discussing about here so your guess and my guess is as good as any.
Couldn't agree more. It's a widely used and honored rule of thumb but as stated above, numbers not based on scientific experiments and evidence are simply anecdotal and their only purpose is just that, being a rule of thumb. We can argue to death here all day one way or the other and it won't make a difference until we collect hard evidence.
Agreed as well. We both expressed our opinions and it's up to the OP to take what he wants.
This is great thank you! I had never delved into the design of an overflow into that detail (I just take what the manufacturer says for granted) and this actually enriches my education. That's why I like engaging into these conversations, you always gain something. From Bernoulli's equation there, and for the same weir length, you definitely have a proportional correlation between flow rate and water height. So in that sense, yes you would have to take more water in the sump.
Thanks again for the response
Cheers to me! I deserve this! LOL
Thanks again for the response
Cheers to me! I deserve this! LOL
