Skimming 101
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btuck
Well-known member
Just when you think you know a little something about skimming...you people come in and take me to school. Good information though, and now I'm a little smarter than I used to be. As far as the seaclone goes. I would say its lack of performance would come from a multitude of problems not just the turbulence of the bubbles. The lack of contact time, small pump, and the poor design of the skimmer would also contribute I would think.
Ok let put up a little summery of what we have covered.
the ideal amount of time you want to treat your tank water in a day is a minimium of two times. Now you can just do a I have a pump and it feeds the skimmer 300 gallons and hour and the tank is 100 gallons, so I turn my tank 3 times an hour. It doesnt work like that.To properly skim your tank to a purity of 99.99 % the forumal would be (tank gallons/feed pump gph) time 9.2 = the time it takes to fully treat all your water.
Dwell time for the water in the skimmer. How long does the protien laidened water spend in the skimmer chamber getting cleaned. You figure this out by dividing the amount of water the skimmer holds by the feed pumps gph rate. The longer the dwell time the better the cleaning the water will recieve. This is a function of the pump delivering the water and the diameter of the skimmer.
Dwell time for the air injected into the skimmer. How long does the air in the skimmer stay in contact with the water molecules. This is a function of the rise time of the air bubbles from the entry point to thier realease via the cup. This is a function of the turbulance and water flow with in the skimmer as that restricts (or slows down it rise) its rising. It is also a function of the height of the skimmer, the higher the height the longer the air bubble has to go to get out.
The bombardment rate. This is the rate that the protien/organic mole gets hit (mechanically strip) the the protien/organic from the water mole. This is a function of the dwell time of the water and the dwell time of the air. So the forumla is the amount of time the water spends in the skimer devided by the amount of time the air bubble spends in the skimmer.
The volume of air. This is the amount of air as compared to the amount of water in the skimmer. The forumla is that the air volume should be 20% of the total water volume. So if you have a skimmer that holds 5 gallons of water, you should only have 1 gallon of air in thier. If you have more air then this figure in your skimmer the bubble will join togehter and be to large and thus will not hold as much of the protiens/organics on their surface. Also it will reduce your bombardment rate as thier wont be as many bubbles hitting the water moles.
Configuration. The injection points for both water and air are also critical for the skimmer to work efficiently. Example of this would be, if the water enters the top of the skimmer and exits the bottom and that your air enters the bottom and leave via the top, it would mean that all water must pass through the air bubbles in order to leave the skimmer. This method is the best. If the water and the air are injected at the same point, then your bombardment rate is reduced as the air bubble will travel with the same water mole all the way to its exit, thus it only hits a few water moles instead of many.
Contact time. Since the function of a protien skimmer is to first mechanically strip the protien/organics from the water mole and then to chemically attract the protien/organic to the surface of the air bubble, it is important for the organic/protien to pend as much time in contact with the air bubbles. Now with some protiens it take a long time for them to actually bond to the surface of the bubbles, so the more the better.
Violence in the skimmer. No matter what method the skimmer applies to make bubbles and or put water into the skimmer. it can not be violent. If it is it will cause the air bubbles to break (thus loose thier attached protiens) join together (thus make larger bubbles that loose the amount of surface area available for protiens).
well i think I covered the gist, let me know if I missed soemthing
Mike
the ideal amount of time you want to treat your tank water in a day is a minimium of two times. Now you can just do a I have a pump and it feeds the skimmer 300 gallons and hour and the tank is 100 gallons, so I turn my tank 3 times an hour. It doesnt work like that.To properly skim your tank to a purity of 99.99 % the forumal would be (tank gallons/feed pump gph) time 9.2 = the time it takes to fully treat all your water.
Dwell time for the water in the skimmer. How long does the protien laidened water spend in the skimmer chamber getting cleaned. You figure this out by dividing the amount of water the skimmer holds by the feed pumps gph rate. The longer the dwell time the better the cleaning the water will recieve. This is a function of the pump delivering the water and the diameter of the skimmer.
Dwell time for the air injected into the skimmer. How long does the air in the skimmer stay in contact with the water molecules. This is a function of the rise time of the air bubbles from the entry point to thier realease via the cup. This is a function of the turbulance and water flow with in the skimmer as that restricts (or slows down it rise) its rising. It is also a function of the height of the skimmer, the higher the height the longer the air bubble has to go to get out.
The bombardment rate. This is the rate that the protien/organic mole gets hit (mechanically strip) the the protien/organic from the water mole. This is a function of the dwell time of the water and the dwell time of the air. So the forumla is the amount of time the water spends in the skimer devided by the amount of time the air bubble spends in the skimmer.
The volume of air. This is the amount of air as compared to the amount of water in the skimmer. The forumla is that the air volume should be 20% of the total water volume. So if you have a skimmer that holds 5 gallons of water, you should only have 1 gallon of air in thier. If you have more air then this figure in your skimmer the bubble will join togehter and be to large and thus will not hold as much of the protiens/organics on their surface. Also it will reduce your bombardment rate as thier wont be as many bubbles hitting the water moles.
Configuration. The injection points for both water and air are also critical for the skimmer to work efficiently. Example of this would be, if the water enters the top of the skimmer and exits the bottom and that your air enters the bottom and leave via the top, it would mean that all water must pass through the air bubbles in order to leave the skimmer. This method is the best. If the water and the air are injected at the same point, then your bombardment rate is reduced as the air bubble will travel with the same water mole all the way to its exit, thus it only hits a few water moles instead of many.
Contact time. Since the function of a protien skimmer is to first mechanically strip the protien/organics from the water mole and then to chemically attract the protien/organic to the surface of the air bubble, it is important for the organic/protien to pend as much time in contact with the air bubbles. Now with some protiens it take a long time for them to actually bond to the surface of the bubbles, so the more the better.
Violence in the skimmer. No matter what method the skimmer applies to make bubbles and or put water into the skimmer. it can not be violent. If it is it will cause the air bubbles to break (thus loose thier attached protiens) join together (thus make larger bubbles that loose the amount of surface area available for protiens).
well i think I covered the gist, let me know if I missed soemthing
Mike
Great!Let's go build some Skimmers!!!
Mike I got 2ft of 200mm(less 8") acrylic tube for the main body the other day.
I'm planning a cylindrical mixing box the biggest I could fit in my sump for the base.
And I'm limited a height of 40" under my tank. I have no idea whether to use venturi needle of whatever is the best I could get my hands on.
I'll try to start a new thread for this!Please help!Thanks!
Joey
Mike I got 2ft of 200mm(less 8") acrylic tube for the main body the other day.
I'm planning a cylindrical mixing box the biggest I could fit in my sump for the base.
And I'm limited a height of 40" under my tank. I have no idea whether to use venturi needle of whatever is the best I could get my hands on.
I'll try to start a new thread for this!Please help!Thanks!
Joey
jlehigh
Hermit D Crab
Mike that is the best summary I have seen on the subject! Great job!
Glad I found this thread.
Im using an AP902 from Deltec for my 250G tank and was previous pushing thru 500GPH. Have since adjusted it down to about 300 GPH which will naturally increase the dwell time.
Bubble production on the skimmer is provided by 2 x Eheim 1262 recirculating powerheads.
Will see if more skimmate is being produced by the lower flowrate thru the skimmer as this is the only 'measurable' effect of the changes. IF more skimmate than before means its more effective at stripping the organics from the water. Right?
Im using an AP902 from Deltec for my 250G tank and was previous pushing thru 500GPH. Have since adjusted it down to about 300 GPH which will naturally increase the dwell time.
Bubble production on the skimmer is provided by 2 x Eheim 1262 recirculating powerheads.
Will see if more skimmate is being produced by the lower flowrate thru the skimmer as this is the only 'measurable' effect of the changes. IF more skimmate than before means its more effective at stripping the organics from the water. Right?
Lorbear
Member
Skimming
Hello!
I was recently given a piece of artificial coral. The manufacturer guarantees it to b e completely safe for saltwater (Nature's Image). Shortly thereafter, my skimmer stopped producing foam. The manufacturere said I should completely clean the skimmer which I did. It produces bubbles as before but no foam! I then re-installed my older Aqua-Medic air driven skimmer. It also produces bubbles as ever but no foam!! My corals, fish and tridacnas all look great and there are no signs of any problems! Any comments?
Would appreciate any suggestions!
Hello!
I was recently given a piece of artificial coral. The manufacturer guarantees it to b e completely safe for saltwater (Nature's Image). Shortly thereafter, my skimmer stopped producing foam. The manufacturere said I should completely clean the skimmer which I did. It produces bubbles as before but no foam! I then re-installed my older Aqua-Medic air driven skimmer. It also produces bubbles as ever but no foam!! My corals, fish and tridacnas all look great and there are no signs of any problems! Any comments?
Would appreciate any suggestions!
Anthony Calfo
Well-known member
Lorbear... over what period of time has foam ceased to be produced? Are we talking a couple of days... or a few weeks?
the artificial decoration likely had nothing to do with it BTW.
Just putting ones hand in the tank (breaking the proteinaceous film/surface) will interrupt skimmate production for many hours.
The presence of a low pressure weather front also increases bubble size (production) and decreases skimmate production (you will often notice that skimmers "die" when the barometric pressure drops)
And any of a number of changes to the sump/level, flow, etc of the system could have jammed up this skimmer leading you to think that the addition of the ornament around the same time has caused the (foam) cessation.
Do look at these options for starters.
test the theory by adding a bit of water conditioner that has colloids in it (AKA "bandage in a bottle", "skin conditioners"... such as Novaqua from Kordon)
Kindly, Anthony
the artificial decoration likely had nothing to do with it BTW.
Just putting ones hand in the tank (breaking the proteinaceous film/surface) will interrupt skimmate production for many hours.
The presence of a low pressure weather front also increases bubble size (production) and decreases skimmate production (you will often notice that skimmers "die" when the barometric pressure drops)
And any of a number of changes to the sump/level, flow, etc of the system could have jammed up this skimmer leading you to think that the addition of the ornament around the same time has caused the (foam) cessation.
Do look at these options for starters.
test the theory by adding a bit of water conditioner that has colloids in it (AKA "bandage in a bottle", "skin conditioners"... such as Novaqua from Kordon)
Kindly, Anthony
- Joined
- Sep 6, 2004
- Messages
- 109
A little late.. but wouldnt mind adding my 2 cents to Skimming 101.
The name says it all, Skimmer. Very basic.. your skimming a liquid surface for floating debris and other misc organics into a collection cup. We have water that is dirtier than natural reefs. The flow into the skimmer will need to recirculate in order to get the best performance with microgravity pushing skimmate to the top by the rise of air bubbles. When you put an adundance of air bubbles together, you get bigger bubbles with a larger surface area. Some bubbles collide and bounce away. The output of the flow is usually met by a sponge that will grab larger debris before it flows back into the tank. A well maintained skimmer will give you its best performance. You always want the inside of the skimmer to be clear of algae buildup or gunk at the neck. If there is algae on these walls, you are defeating the purpose and the bubbles will burst before they get to the top. The design of a skimmer is what makes its performance a good one. I also feel that slower flow is the way to go. If you have higher flow, you are rushing the bubbles which decreases the amount of bubbles before it gets to the top.
Another positive outcome from a skimmer is the ability to create chemical reactions with Oxygen, hence the higher PH levels. In a natural reef, the mixture of 02 is met by tidal waves, storms... called air-sea interaction. Animals and microorganisms (bacteria) use oxygen to carry out metabolic activities increasing the overall health of your aquarium.
The name says it all, Skimmer. Very basic.. your skimming a liquid surface for floating debris and other misc organics into a collection cup. We have water that is dirtier than natural reefs. The flow into the skimmer will need to recirculate in order to get the best performance with microgravity pushing skimmate to the top by the rise of air bubbles. When you put an adundance of air bubbles together, you get bigger bubbles with a larger surface area. Some bubbles collide and bounce away. The output of the flow is usually met by a sponge that will grab larger debris before it flows back into the tank. A well maintained skimmer will give you its best performance. You always want the inside of the skimmer to be clear of algae buildup or gunk at the neck. If there is algae on these walls, you are defeating the purpose and the bubbles will burst before they get to the top. The design of a skimmer is what makes its performance a good one. I also feel that slower flow is the way to go. If you have higher flow, you are rushing the bubbles which decreases the amount of bubbles before it gets to the top.
Another positive outcome from a skimmer is the ability to create chemical reactions with Oxygen, hence the higher PH levels. In a natural reef, the mixture of 02 is met by tidal waves, storms... called air-sea interaction. Animals and microorganisms (bacteria) use oxygen to carry out metabolic activities increasing the overall health of your aquarium.
Good post invincible!. I dont know if a recirc is really the cats meow or not. Recirc the water/air mix will give you some more contact time and dwell, but going through the pump again would seem to have a negative effect of protiens binding to the bubbles. How much would be dis associated I am not sure.
If one takes these basice laws to govern skimming I think it should paint a pretty clear picture on how smple a skimmer should really be
Fkadir thats pretty much the concept, the more time you allow the bubbles to interface with the skimmer the more they will strip the water with in the skimmer. Also if you do the math on your skimmer, as in gallons of water in the tank times gph on the skimmer pump times the co-efficient rate of 9.2 would mean that you are turning your tank a little over three times a day or every 7.6 hours. So if you wanted you could even drop it down farther if you wished.
Mike
If one takes these basice laws to govern skimming I think it should paint a pretty clear picture on how smple a skimmer should really be
Fkadir thats pretty much the concept, the more time you allow the bubbles to interface with the skimmer the more they will strip the water with in the skimmer. Also if you do the math on your skimmer, as in gallons of water in the tank times gph on the skimmer pump times the co-efficient rate of 9.2 would mean that you are turning your tank a little over three times a day or every 7.6 hours. So if you wanted you could even drop it down farther if you wished.
Mike
Kensn
Well-known member
May I get an opinion on this idea? I am in the process of getting a new sump built. This is only to house the skimmer, as I have a seperate fuge area. My thought was to have the skimmer pull out water from the area behide the first baffle where the water enters the sump so I would only get tank water in and none from the outlet of the skimmer. I guess my reasoning for this was to make sure I had the "dirtiest" water going into the skimmer and not reskim water that had already, hopefully, been semi stripped. Does this make a good reasoning, no matter how efficent your skimmer is, might as well give it the dirtiest water to pull from.
Feedback please.
Feedback please.
Scooterman
Well-known member
MINIATUS said:
First I drilled all of the air fittings to allow for more air, removed the two back flow tubes that were installed, used a ball valve to control the water inlet, not major changes.
Tiny Giants
Member
Okay based on the info in this thread, here is my calcs for my tank. Any thoughts?
Ideal skimming would be 2 - 3 tank volumes a day.
The formula for this is:
(total tank and sump volume / feed rate gph) X 9.2 (this is purity coefficent that will yield 99.9% processed water) = hours till processed
The goal of 2 - 3 times a day means we need to process every 8 - 12 hours.
In my tank it works like this:
( 150 g / flow rate ) 9.2 = 12
150 g / flow rate = 12/9.2
150 g / flow rate = 1.30
150 g = 1.30 flow rate
150 g / 1.30 = flow rate
115 gph = flow rate
This means by feeding my skimmer 115 gph, I will 99.9 % process my tank every 12 hours.
Dwell time is another issue. It is based on this formula:
skimmer volume / gpm = dwell time for water
Dwell time alone is not enough. We also want the air bubble dwell time. With this info we can figure bombardment rate
I have no idea how to get an accurate measure of a bubbles actual dwell time. So I pulled a number out of thin air of 15 seconds in 24" counter current design.
In my tank:
Using a 2 gpm feed into 11 g skimmer (12 dia X 24 tall) I get a dwell time of 5.5 minutes.
5.5 minutes = 330 seconds
bombardment rate = 330/15 = 22.
Bombardment rate = water dwell in seconds / air dwell in seconds
A perfect goal is considered to be 10,right?
I am way off of the goal, but is it bad?
Thanks for any help you can give.
Dale
Ideal skimming would be 2 - 3 tank volumes a day.
The formula for this is:
(total tank and sump volume / feed rate gph) X 9.2 (this is purity coefficent that will yield 99.9% processed water) = hours till processed
The goal of 2 - 3 times a day means we need to process every 8 - 12 hours.
In my tank it works like this:
( 150 g / flow rate ) 9.2 = 12
150 g / flow rate = 12/9.2
150 g / flow rate = 1.30
150 g = 1.30 flow rate
150 g / 1.30 = flow rate
115 gph = flow rate
This means by feeding my skimmer 115 gph, I will 99.9 % process my tank every 12 hours.
Dwell time is another issue. It is based on this formula:
skimmer volume / gpm = dwell time for water
Dwell time alone is not enough. We also want the air bubble dwell time. With this info we can figure bombardment rate
I have no idea how to get an accurate measure of a bubbles actual dwell time. So I pulled a number out of thin air of 15 seconds in 24" counter current design.
In my tank:
Using a 2 gpm feed into 11 g skimmer (12 dia X 24 tall) I get a dwell time of 5.5 minutes.
5.5 minutes = 330 seconds
bombardment rate = 330/15 = 22.
Bombardment rate = water dwell in seconds / air dwell in seconds
A perfect goal is considered to be 10,right?
I am way off of the goal, but is it bad?
Thanks for any help you can give.
Dale
Last edited:
Tiny Giants
Member
Well based on this thread (and one at the other site), I built a spreadsheet to help with all of these calculations.
Something that came up over there was bubble dwell time versus water dwell time. A chemical engineer debated the point that it was the air contact with water for 120 seconds that bonded with the stuborn organics. The water dwell of 120 seconds would not allow this bonding to occur as the bubbles were constantly leaving the water column before the stuborn bonds could happen.
This sheet will calculate the air volume required to meet the 13% Saturation.
It does all of the messy conversions on the fly (cubic inches - gallons, GPH - GPM, and so on).
It calculates water dwell time taking into consideration the volume of air in the skimmer.
Bubble dwell is calculated for a counter current skimmer.
For those that employ a recirc pump on the skimmer body, it calculates the recirc effect on the bubble and associated times.
While calculating this I found it interesting that the airpump does not need to be a brute if you keep the bubble suspended in the water column.
Let me know if you find any errors in my calculations.
The other web site has the sheet for download. This site will not allow a .xls upload.
Dale
Something that came up over there was bubble dwell time versus water dwell time. A chemical engineer debated the point that it was the air contact with water for 120 seconds that bonded with the stuborn organics. The water dwell of 120 seconds would not allow this bonding to occur as the bubbles were constantly leaving the water column before the stuborn bonds could happen.
This sheet will calculate the air volume required to meet the 13% Saturation.
It does all of the messy conversions on the fly (cubic inches - gallons, GPH - GPM, and so on).
It calculates water dwell time taking into consideration the volume of air in the skimmer.
Bubble dwell is calculated for a counter current skimmer.
For those that employ a recirc pump on the skimmer body, it calculates the recirc effect on the bubble and associated times.
While calculating this I found it interesting that the airpump does not need to be a brute if you keep the bubble suspended in the water column.
Let me know if you find any errors in my calculations.
The other web site has the sheet for download. This site will not allow a .xls upload.
Dale
NaH2O
Well-known member
- Joined
- Jan 25, 2004
- Messages
- 8,568
The calculator can also be found here on this thread: Skimmer Calculator
Tiny Giants
Member
NaH2O said:
I was working with crazzyreefer on the development of my sheet at the other site. His sheet was first. It is not the same as the one he posted. There are differences in the design his calculator is made for (I liked his sheet, but it did not fit my design goals). He is playing with a new design he calls convection. Mine is based on counter current design.
Dale
Boomer
Well-known member
I just saw this thread so I have not read hardly any of the posts but have some info.
This year in FAMA there was a 3-part series on all the modern skimmers and how they work and compare.
and
Protein Skimming: How It Works
http://web.archive.org/web/20010309054900/http://home.mweb.co.za/jv/jv79/reef/skimmers2.html
Allot of the tech info Mojo posted can be found in Pete's book. It is a very mathamatically book.
Aquatic Systems Engineering by Peter Escobol
A Review
http://www.calgaryaquariumsociety.com/Articles/Aquatic_Systems_Engineering.html
I forgot there is also an extensive review in Spott's book
Seawater Aquariums; The Captive Environment
Dale nice job
This year in FAMA there was a 3-part series on all the modern skimmers and how they work and compare.
and
Protein Skimming: How It Works
http://web.archive.org/web/20010309054900/http://home.mweb.co.za/jv/jv79/reef/skimmers2.html
Allot of the tech info Mojo posted can be found in Pete's book. It is a very mathamatically book.
Aquatic Systems Engineering by Peter Escobol
A Review
http://www.calgaryaquariumsociety.com/Articles/Aquatic_Systems_Engineering.html
I forgot there is also an extensive review in Spott's book
Seawater Aquariums; The Captive Environment
Dale nice job
Last edited:
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