GPH, lets just cut through all the miss information

tim_s · 01/28/2012, 05:01 PM

Hi,

So I have had sumps before and I have yet had anyone realistically give me information about GPH on return pumps.

The only advise I have ever received was "More is better" is this true, can more not be harmful?

Example: I have just bought a used setup (As I am moving within a year, this is my introduction into Salt Water) it is a 75G display tank with a 30G sump. I caught the owner just shortly after piecing out the setup and I am without the return pump.

Originally the setup had a RIO 2500 but I also have a MAG 36 aka 3600 GPH, I can split the return, but could this be damaging to corals, sea anemone - fish?

seapug · 01/28/2012, 05:09 PM

It all depends on how much flow your drains can handle. If you exceed their capacity the display will overflow. I doubt the drains on that tank will be able to handle 3600 gph.

Alex T. · 01/28/2012, 05:24 PM

While it's true that you need good flow in a reef tank, running that much through the sump would almost render it useless. If you have a skimmer that processes 500 gallons per hour and a return pump that's pulling 3,600 gallons per hour, it's easy to figure out that larger volumes of dirty water are passing the skimmer and other filer media faster than you could possibly process it. Plus, you'd be paying more electricity running the pumps you mention with less clean water...not very efficient to say the least.

You should look for a return pump around 2-5 times the tank volume per hour and your skimmer will work better. That means about 300 gallons per hour maximum. Look for efficient power heads in the display tank to make up for water movement, not the return pump. You'll save on electric and have a cleaner tank. Running 3,600 gallons of water through a sump for a 75 gallon display is not overkill. It's bad design. I run an Iwaki 30 external RLXT on my 195 reef tank. It's 960 gph at 4 foot head pressure...which is roughly 4.9 times the tank turnover. I may even bring it down to an Iwaki 20 RLXT.

HTH

scarface70706 · 01/28/2012, 05:26 PM

well rule of thumb is 3-5X's your DT. ie: 75g X 5 = 375 gph. i have a 90 gallon DT and i use to run a mag 9.5 all the way open and my overflow kept up. the mag 9.5 is way more then enough flow for me at first so i installed a ball valve to control the flow better so my socks, fuge, and skimmer worked more efficiently. a few months ago i added 2 reactors to my return line's manifold and now im considering upgrading my pump since the new addition of bio pellets need a little bit more flow then the gfo i use to run so my turn over rate is pretty slow. i think a mag 9.5 would be perfect for your tank size. stick a ball valve on it and you will be good to go. also when going bigger it allows room for you to grow ie: making a manifold for other equipment, bigger tank, etc. also you need to see what your return area is in the sump so you can see what pump can fit. good luck

Alex T. · 01/28/2012, 05:39 PM

Additionally, unless you plan on drilling a couple of 2 inch drains in the tank, you'll never pull 3,600 GPH to your sump.

tim_s · 01/28/2012, 05:41 PM

The overflow is a coast to coast the owner has giving me videos of the tank running using a return pump RIO 2500, the skimmer is external and rated at 125G. The 2 X over flow pipes are 1.5" and within the videos the overflow is falling less than half full. - but the advise being provided is sound I will go with a MAG 9.5

tim_s · 01/28/2012, 05:45 PM

Quote:

Originally Posted by Alex T.

Additionally, unless you plan on drilling a couple of 2 inch drains in the tank, you'll never pull 3,600 GPH to your sump.

I have 3" drain capacity.

Alex T. · 01/28/2012, 06:00 PM

Two 1 1/2" drains doesn't equal a 3 inch drain's capacity. In fact, one two inch drain would be more efficient. That said, what you have is more than enough for your tank. You don't need to try and maximize the drain line's capacity simply because it's available. Having the quiet draining of drains that are not being worked to capacity is nice.

Read here if you want the lo-down...

http://wetwebmedia.com/SystemPIX/Plu...Oneinchart.htm

tim_s · 01/28/2012, 06:01 PM

OK! I see what has happened - i apologies.

The MAGs naming convention is in Gallons i.e. the MAG 36a is a 3600 GPH device, where-as the RIO 2500 is 2500 LPH meaning at a 4 foot head travel the pump would only be pushing 529 GPH

*BIG* difference.

tim_s · 01/28/2012, 06:04 PM

Quote:

Originally Posted by Alex T.

Two 1 1/2" drains doesn't equal a 3 inch drain's capacity. In fact, one two inch drain would be more efficient. That said, what you have is more than enough for your tank. You don't need to try and maximize the drain line's capacity simply because it's available. Having the quiet draining of drains that are not being worked to capacity is nice.

Read here if you want the lo-down...

http://wetwebmedia.com/SystemPIX/Plu...Oneinchart.htm

Oh I agree, I mean clearly speaking it is obvious that if my skimmer can only process 125G and I am pushing 3000 at a 4' head, I am clearly just cycling dirty water, possibly great for oxygenating the water but there is many more - less costly methods of achieving this. - I was just hung up on how the previous owner appeared to be pushing 2000 <~ GPH and getting away with it.

csmfish · 01/29/2012, 09:38 AM

I dont buy that fact that slower water for the skimmer is good. Its not like the dirty water stays in the sump if you go slower. I actually think the faster you cycle the display water the more dirty the water is for the skimmer. If you turn over 3,000 GPH, that will keep the dirty water in the tank AND in the sump. Remember also that the dirty water from the tank goes into the skimmer and out comes the clean which then mixes with the dirty diluting it. If that diluted water is leaving the sump at a slow rate, then you have cleaner water for the skimmer to clean, rather than high flow well mixed dirty water. Now, if you put the skimmer outlet into another compartment, you might have something. As far as socks and other equipment, thats another story, yea, slower would be better.

robertcedgar · 01/29/2012, 09:58 AM

Just a thought on the matter. Within reason, with the exception of a sump-based refugium, lots of flow through the sump is not necessarily a bad thing. So long as your overflow(s) can handle the pace, your filter socks, sponges, etc., will catch suspended gunk. When cleaned as part of your maintenance routine, it would follow that more bad stuff would be exported from the system with a high power pump via the cleaning of filter socks, etc. I run a 2,000 GPH rated pump for my sump in my 130. In actuality, when figuring the length of the plumbing and "t" to the chiller, it's probably running somewhere in the area of 1,200 GPH return to the tank. So, within reason, I believe that it's a good thing to have a strong return pump. JMO.

tkeracer619 · 01/29/2012, 10:40 AM

Quote:

Originally Posted by csmfish

I dont buy that fact that slower water for the skimmer is good. Its not like the dirty water stays in the sump if you go slower.

The top surface of water that is drained to the sump is the dirtiest water in the tank. Going faster does not increase the amount of stuff you pull in. Its marginal and I am not sure there is any solid evidence but trial and error would support that lower flow (to a point) increases skimmer output.

username in use · 01/29/2012, 10:50 AM

Run the minimum required through your sump (3-5x the DT), then supplement in tank flow with powerheads. The power needed to create all your flow with return pumps is far more than what is needed to create the same gph in the tank with prop pumps.

Playa-1 · 01/29/2012, 11:10 AM

I suspect a high volume sump, oversized drain and return setup is usually a misguided attempt at a closed loop system. IMO, it's a waste of energy/money to pump excess water volume thru the sump. I would keep it to the lower end of the scale thru the sump. Get the additional water movement from other sources.

csmfish · 01/29/2012, 12:22 PM

Quote:

Originally Posted by tkeracer619

The top surface of water that is drained to the sump is the dirtiest water in the tank. Going faster does not increase the amount of stuff you pull in. Its marginal and I am not sure there is any solid evidence but trial and error would support that lower flow (to a point) increases skimmer output.

I agree that the top water is the dirtiest, but, if it is going in slow at 100% dirt, getting skimmed at, oh, say 50%, then you have 50% mixing with 100%. What happens with low flow and the mixed gets back into the skimmer, and so on and so on?

If you have a 90% dirty water flow at a large amount of turn over, then you flush out the diluted quicker. Does that equal the same as the above, or? I think that would be a better option for the skimmer to crab more dirty water.

Finally, the only way I see the slow water working is if, like I said, you have the skimmer clean output going to another chamber away from the input chamber. This way you can run at the skimmer speed and always have 100% dirty water.

Quote:

Originally Posted by username in use

Run the minimum required through your sump (3-5x the DT), then supplement in tank flow with powerheads. The power needed to create all your flow with return pumps is far more than what is needed to create the same gph in the tank with prop pumps.

I know your not talking about me, but, just wanted to say to the OP that I never declare running a 3,000GPH pump was the right choice, just stating flow "characteristics" for the skimmer to give you ideas.

Tat2demon · 01/29/2012, 02:47 PM

I don't know why this has continuously been debated year after year. Its common sense.

A skimmer pump with always draw the same amount in weather you run 1 gph or 10000 gph through your sump. Also a skimmer only takes out a small fraction of the junk in your water. Its not like the output is crystal clear, sterilized water and certainly nowhere near %50 cleaned. I would be surprised if a skimmer removes even %2 of of what goes in each pass. A skimmer with perform the same no matter how fast your sump is.

However as others have already said, you probably don't want to depend on your sump for your in tank flow. It much easier to achieve the best flow by using power heads or a CL system.

reefgeezer · 01/29/2012, 02:56 PM

My sump is 16" X 30" and I have about 600 going through it on most days. I use a Panworld 50PX-X pump that is capable of ~1100 gph @ 4'. When I run it wide open, micro-bubbles become an issue. In addition, my skimmer doesn't produce as much skimmate.

I've played with the flow rate to see what worked best for my tank. That would be my advice. However, I'd have to guess that the sweet spot will be somewhere between 500 and 1000 GPH. Buying a pump capable of pumping much more than that might be a waste of money and space.

csmfish · 01/29/2012, 03:24 PM

Quote:

Originally Posted by Tat2demon

I don't know why this has continuously been debated year after year. Its common sense.

A skimmer pump with always draw the same amount in weather you run 1 gph or 10000 gph through your sump. Also a skimmer only takes out a small fraction of the junk in your water. Its not like the output is crystal clear, sterilized water and certainly nowhere near %50 cleaned. I would be surprised if a skimmer removes even %2 of of what goes in each pass. A skimmer with perform the same no matter how fast your sump is.

However as others have already said, you probably don't want to depend on your sump for your in tank flow. It much easier to achieve the best flow by using power heads or a CL system.

I guess you didnt hear my part about recirculating clean water be it 50% (which was just an example thank you mr take it to the limits) or 2% but thats okay. Clean water from the skimmer mixed with low flow incoming (I am talking water from the tank to the portion of glass that holds the skimmer) = diluted water before going into the skimmer pump. Whats better, diluted water, whatever the percentage, to skim or pure dirty water? Lets wait for common sense to kick in before answering.

Drae · 01/29/2012, 03:25 PM

Fwiw, there is no debate over this subject. I shoot for 5x the total water volume (sump and display) out of my returns. End of story. Any more is unnecessary imho. And skimmers do have a sweet spot in water flow. Like mentioned above, if I open my valves fully it takes almost twice the time to produce a half cups skimmate (the skimmer cups, not 8oz). I've experimented this subject myself and was amazed by the difference. Try to match skimmer and return pumps as close as possible. Trust me it works out.

Drae · 01/29/2012, 03:33 PM

Example; the sedra 5000 is around 500 gph rated for tanks around 140 gallons when used on a skimmer. 140 x 4= 560. A 140 gallon tank with 560 ACTUAL gallons of flow would be perfect imho, and ime's. Just food for your brain. And my 2¢

reefgeezer · 01/29/2012, 04:30 PM

I'd agree that 5-7X is a good place to start and is most likely to be near the sweet spot. Buying a pump that is capable of 1000 gph or so might be advisable just to give you a little excess capacity and to account for head loss due to plumbing and organic build-up in the lines.

Tat2demon · 01/29/2012, 04:40 PM

Quote:

Originally Posted by csmfish

I guess you didnt hear my part about recirculating clean water be it 50% (which was just an example thank you mr take it to the limits) or 2% but thats okay. Clean water from the skimmer mixed with low flow incoming (I am talking water from the tank to the portion of glass that holds the skimmer) = diluted water before going into the skimmer pump. Whats better, diluted water, whatever the percentage, to skim or pure dirty water? Lets wait for common sense to kick in before answering.

First, 50% was your example. Don't use it if you're going to berate people for using it after you.

My point is, many people act like a skimmer cleans every bit of gunk out of the water and use that as the reason to have a sump slow enough to for the skimmer to uptake every bit of water that comes through. I believe we are agreeing on the dilution however I may not have stated it properly.

Also, for the people that say "I get better results at slower rates so its a fact!". Good for you. But remember that because it works best for you, its not a fact.

I have run 500 gph through my sump and am currently running 3500 (my main flow until I get my CL pump) and have seen no difference what so ever in the output of my SWC. Tons of microbubbles from the skimmer that make it into the tank but no difference in collection.

Now with that being said I most certainly prefer a slower sump for no other reason than for noise and bubble reduction.

csmfish · 01/29/2012, 09:43 PM

Quote:

Originally Posted by Drae

Fwiw, there is no debate over this subject.

And thats why you get beat up in your posts and your threads get shut down. Then say you proved a point to your wife when you didnt even coherently prove a point to us!?

Quote:

Originally Posted by Tat2demon

First, 50% was your example. Don't use it if you're going to berate people for using it after you.

My exact words were "at, oh, say 50%," . I would have thought the way I worded it people knew I was just pulling a number out of the air and it would be used as an example, aka common sense.

You even said

"I don't know why this has continuously been debated year after year. Its common sense."

I guess people who debate it still do not have common sense?

I was just point it out back at you bro, thats all.

Now, my theory is correct, diluted water is diluted water. I never said I have real world results and I SURE dont see anyone explaining the scientific theory behind why diluted water gets cleaned better than pure dirty water whatever the flow. So, until someone explains that, i guess NONE of us have any common sense, ehy, lol??

jerpa · 01/30/2012, 08:12 AM

I think the total efficiency of skimmers make this a moot point. They remove nowhere near 100% of the waste in the water so there will always be "dirty" water left after skimming. You could argue that with a surface skimming overflow lower flow is better. The lower flow means the sheet of water entering the overflow is thinner. This improves surface skimming so the water your pulling from the tank has a greater concentration of organic matter the skimmer can remove. With too high of a flow, or a shorter overflow, you will pull more water from beneath the surface leaving a film of skimmable gunk on top of the water.

Either way I shoot for 3-5x the tank volume to minimize bubbles and noise in my sump.

01/28/2012, 05:01 PM	#1
tim_s Registered Member Join Date: Dec 2011 Posts: 36	GPH, lets just cut through all the miss information Hi, So I have had sumps before and I have yet had anyone realistically give me information about GPH on return pumps. The only advise I have ever received was "More is better" is this true, can more not be harmful? Example: I have just bought a used setup (As I am moving within a year, this is my introduction into Salt Water) it is a 75G display tank with a 30G sump. I caught the owner just shortly after piecing out the setup and I am without the return pump. Originally the setup had a RIO 2500 but I also have a MAG 36 aka 3600 GPH, I can split the return, but could this be damaging to corals, sea anemone - fish?

01/28/2012, 05:09 PM	#2
seapug Registered Member Join Date: Dec 2006 Location: 4980 ft. Posts: 7,954 Blog Entries: 1	It all depends on how much flow your drains can handle. If you exceed their capacity the display will overflow. I doubt the drains on that tank will be able to handle 3600 gph. __________________ insert clever saying here. Current Tank Info: 200 gallon custom Marineland DD peninsular tank. LPS dominated mixed reef. Previous 90 gallon mixed reef TOTM April 2009.

01/28/2012, 05:24 PM	#3
Alex T. Registered Member Join Date: Nov 2008 Location: New Jersey Posts: 1,803	While it's true that you need good flow in a reef tank, running that much through the sump would almost render it useless. If you have a skimmer that processes 500 gallons per hour and a return pump that's pulling 3,600 gallons per hour, it's easy to figure out that larger volumes of dirty water are passing the skimmer and other filer media faster than you could possibly process it. Plus, you'd be paying more electricity running the pumps you mention with less clean water...not very efficient to say the least. You should look for a return pump around 2-5 times the tank volume per hour and your skimmer will work better. That means about 300 gallons per hour maximum. Look for efficient power heads in the display tank to make up for water movement, not the return pump. You'll save on electric and have a cleaner tank. Running 3,600 gallons of water through a sump for a 75 gallon display is not overkill. It's bad design. I run an Iwaki 30 external RLXT on my 195 reef tank. It's 960 gph at 4 foot head pressure...which is roughly 4.9 times the tank turnover. I may even bring it down to an Iwaki 20 RLXT. HTH __________________ 72x26x24, custom sump, BK SM 200, 4 Vortech MP40s, 1 Tunze 6105, (3) 250 Watt Radiums in Lumenmax Elite Reflectors, Galaxy ballasts, (2) 60" Super Actinic VHOs, 2 Kessil a150s, Apex controlled. Current Tank Info: Currently in reboot mode

01/28/2012, 05:39 PM	#5
Alex T. Registered Member Join Date: Nov 2008 Location: New Jersey Posts: 1,803	Additionally, unless you plan on drilling a couple of 2 inch drains in the tank, you'll never pull 3,600 GPH to your sump. __________________ 72x26x24, custom sump, BK SM 200, 4 Vortech MP40s, 1 Tunze 6105, (3) 250 Watt Radiums in Lumenmax Elite Reflectors, Galaxy ballasts, (2) 60" Super Actinic VHOs, 2 Kessil a150s, Apex controlled. Current Tank Info: Currently in reboot mode

01/28/2012, 06:00 PM	#8
Alex T. Registered Member Join Date: Nov 2008 Location: New Jersey Posts: 1,803	Two 1 1/2" drains doesn't equal a 3 inch drain's capacity. In fact, one two inch drain would be more efficient. That said, what you have is more than enough for your tank. You don't need to try and maximize the drain line's capacity simply because it's available. Having the quiet draining of drains that are not being worked to capacity is nice. Read here if you want the lo-down... http://wetwebmedia.com/SystemPIX/Plu...Oneinchart.htm __________________ 72x26x24, custom sump, BK SM 200, 4 Vortech MP40s, 1 Tunze 6105, (3) 250 Watt Radiums in Lumenmax Elite Reflectors, Galaxy ballasts, (2) 60" Super Actinic VHOs, 2 Kessil a150s, Apex controlled. Current Tank Info: Currently in reboot mode

01/28/2012, 05:26 PM	#4
scarface70706 Registered Member Join Date: Jul 2011 Posts: 1,364	well rule of thumb is 3-5X's your DT. ie: 75g X 5 = 375 gph. i have a 90 gallon DT and i use to run a mag 9.5 all the way open and my overflow kept up. the mag 9.5 is way more then enough flow for me at first so i installed a ball valve to control the flow better so my socks, fuge, and skimmer worked more efficiently. a few months ago i added 2 reactors to my return line's manifold and now im considering upgrading my pump since the new addition of bio pellets need a little bit more flow then the gfo i use to run so my turn over rate is pretty slow. i think a mag 9.5 would be perfect for your tank size. stick a ball valve on it and you will be good to go. also when going bigger it allows room for you to grow ie: making a manifold for other equipment, bigger tank, etc. also you need to see what your return area is in the sump so you can see what pump can fit. good luck

01/28/2012, 05:41 PM	#6
tim_s Registered Member Join Date: Dec 2011 Posts: 36	The overflow is a coast to coast the owner has giving me videos of the tank running using a return pump RIO 2500, the skimmer is external and rated at 125G. The 2 X over flow pipes are 1.5" and within the videos the overflow is falling less than half full. - but the advise being provided is sound I will go with a MAG 9.5

01/28/2012, 06:01 PM	#9
tim_s Registered Member Join Date: Dec 2011 Posts: 36	OK! I see what has happened - i apologies. The MAGs naming convention is in Gallons i.e. the MAG 36a is a 3600 GPH device, where-as the RIO 2500 is 2500 LPH meaning at a 4 foot head travel the pump would only be pushing 529 GPH BIG difference.

01/29/2012, 09:38 AM	#11
csmfish Moved On Join Date: Dec 2009 Location: VA Posts: 1,055	I dont buy that fact that slower water for the skimmer is good. Its not like the dirty water stays in the sump if you go slower. I actually think the faster you cycle the display water the more dirty the water is for the skimmer. If you turn over 3,000 GPH, that will keep the dirty water in the tank AND in the sump. Remember also that the dirty water from the tank goes into the skimmer and out comes the clean which then mixes with the dirty diluting it. If that diluted water is leaving the sump at a slow rate, then you have cleaner water for the skimmer to clean, rather than high flow well mixed dirty water. Now, if you put the skimmer outlet into another compartment, you might have something. As far as socks and other equipment, thats another story, yea, slower would be better.

01/29/2012, 09:58 AM	#12
robertcedgar Registered Member Join Date: Dec 2009 Location: San Pedro, CA Posts: 236	Just a thought on the matter. Within reason, with the exception of a sump-based refugium, lots of flow through the sump is not necessarily a bad thing. So long as your overflow(s) can handle the pace, your filter socks, sponges, etc., will catch suspended gunk. When cleaned as part of your maintenance routine, it would follow that more bad stuff would be exported from the system with a high power pump via the cleaning of filter socks, etc. I run a 2,000 GPH rated pump for my sump in my 130. In actuality, when figuring the length of the plumbing and "t" to the chiller, it's probably running somewhere in the area of 1,200 GPH return to the tank. So, within reason, I believe that it's a good thing to have a strong return pump. JMO.

01/29/2012, 10:50 AM	#14
username in use Sciencing Daily Join Date: Mar 2009 Posts: 6,560	Run the minimum required through your sump (3-5x the DT), then supplement in tank flow with powerheads. The power needed to create all your flow with return pumps is far more than what is needed to create the same gph in the tank with prop pumps. __________________ Joshua "With fronds like these, who needs anemones?" - Albert Einstein Current Tank Info: multiple nano's sprinkled around the house

01/29/2012, 11:10 AM	#15
Playa-1 Moved On Join Date: Jun 2007 Location: Laguna Niguel, CA Posts: 7,497	I suspect a high volume sump, oversized drain and return setup is usually a misguided attempt at a closed loop system. IMO, it's a waste of energy/money to pump excess water volume thru the sump. I would keep it to the lower end of the scale thru the sump. Get the additional water movement from other sources.

01/29/2012, 02:47 PM	#17
Tat2demon Registered Member Join Date: Mar 2006 Location: Sioux Falls, SD Posts: 833	I don't know why this has continuously been debated year after year. Its common sense. A skimmer pump with always draw the same amount in weather you run 1 gph or 10000 gph through your sump. Also a skimmer only takes out a small fraction of the junk in your water. Its not like the output is crystal clear, sterilized water and certainly nowhere near %50 cleaned. I would be surprised if a skimmer removes even %2 of of what goes in each pass. A skimmer with perform the same no matter how fast your sump is. However as others have already said, you probably don't want to depend on your sump for your in tank flow. It much easier to achieve the best flow by using power heads or a CL system. __________________ Nate cham - "Taste it, if it tastes like poop.....it is." Current Tank Info: 400 gallon in progress. 8x3x2.5

01/29/2012, 02:56 PM	#18
reefgeezer Registered Member Join Date: Dec 2009 Location: Wichita KS Posts: 2,621	My sump is 16" X 30" and I have about 600 going through it on most days. I use a Panworld 50PX-X pump that is capable of ~1100 gph @ 4'. When I run it wide open, micro-bubbles become an issue. In addition, my skimmer doesn't produce as much skimmate. I've played with the flow rate to see what worked best for my tank. That would be my advice. However, I'd have to guess that the sweet spot will be somewhere between 500 and 1000 GPH. Buying a pump capable of pumping much more than that might be a waste of money and space. __________________ John, Current Tank Info: In-process, 90 Gallon SPS Reef

01/29/2012, 03:25 PM	#20
Drae RAIDER NATION! Join Date: Jun 2011 Location: City of sin... Posts: 3,476	Fwiw, there is no debate over this subject. I shoot for 5x the total water volume (sump and display) out of my returns. End of story. Any more is unnecessary imho. And skimmers do have a sweet spot in water flow. Like mentioned above, if I open my valves fully it takes almost twice the time to produce a half cups skimmate (the skimmer cups, not 8oz). I've experimented this subject myself and was amazed by the difference. Try to match skimmer and return pumps as close as possible. Trust me it works out.

01/29/2012, 03:33 PM	#21
Drae RAIDER NATION! Join Date: Jun 2011 Location: City of sin... Posts: 3,476	Example; the sedra 5000 is around 500 gph rated for tanks around 140 gallons when used on a skimmer. 140 x 4= 560. A 140 gallon tank with 560 ACTUAL gallons of flow would be perfect imho, and ime's. Just food for your brain. And my 2¢

01/29/2012, 04:30 PM	#22
reefgeezer Registered Member Join Date: Dec 2009 Location: Wichita KS Posts: 2,621	I'd agree that 5-7X is a good place to start and is most likely to be near the sweet spot. Buying a pump that is capable of 1000 gph or so might be advisable just to give you a little excess capacity and to account for head loss due to plumbing and organic build-up in the lines. __________________ John, Current Tank Info: In-process, 90 Gallon SPS Reef

01/30/2012, 08:12 AM	#25
jerpa Registered Member Join Date: Apr 2011 Location: Pittsburgh Posts: 2,174	I think the total efficiency of skimmers make this a moot point. They remove nowhere near 100% of the waste in the water so there will always be "dirty" water left after skimming. You could argue that with a surface skimming overflow lower flow is better. The lower flow means the sheet of water entering the overflow is thinner. This improves surface skimming so the water your pulling from the tank has a greater concentration of organic matter the skimmer can remove. With too high of a flow, or a shorter overflow, you will pull more water from beneath the surface leaving a film of skimmable gunk on top of the water. Either way I shoot for 3-5x the tank volume to minimize bubbles and noise in my sump.