Importance of Dissolved Oxygen?
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Herefishyfishy
Smart Bass
Algae photosynthesis ceases in the dark and they produce CO2 instead . This also forces down the oxygen levels (and raised the PH)
Right... but why does this have such a huge effect in a tank and not in the open ocean? Obviously, I know it related to the fact that it's a closed system. Bu thow? My only guess is that in the ocean there are currents moving in new oxygenated water from areas of the world that are still lit? But I don't know...
DonW
R.I.P.
Herefishyfishy
Smart Bass
Lowers ph.
Don
Thanks Don, it has been one of those mornings.
As to the Ocean's more stable O2 levels and PH, it is dealing with a vastly larger volume and better wave action. If one measured a tidepool, would most likely show similar results to an aquarium.
Curtswearing
Mantisfreak
No. This was a reef club meeting. I've not seen that IMAC video yet.
Not trying to confuse matters too much here, but what symbiotic thing lives inside corals? We're not strictly speaking of macros in a fuge.
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Boomer
Well-known member
Boy that was allot to read at one sitting
I was scrolling and hoping someone would post Eric's articles. Thanks Curt I might add that is was a well done article by Eric.
To be short
Don.
Pure O2 in a reactor is an absolute no-no. I would not worry about the redox but the O2 going to high. One would have to have an O2 monitor to run such a system to be safe. Second you do not need a reactor with pure O2. A reactor would make it worse, two-fold. 1. allot of mixing. 2. increasing the pressure just by itself increases O2. The higher the psi inside the reactor the more O2 is forced into the water. O3 does almost nothing for increasing O2, until all things are oxidized. Even then, often the O3 just remains O3. The reason behind degassing towers in some aquatic systems using O3. O2 / CO2 skimmer gas thing. You are partially right. It revolves more around the partial pressures of CO2 vs. O2, in water and in the air. They are very different.
Sara
What I'd like to know/understand is why the oxygen levels fall so much at night in tanks but not in the open ocean. In other words, this chart interests me:
For the same reason your pH goes up during the day and down during the night, due to CO2. "Plants" are giving off O2 during the day and consuming O2 at night.
Oceans ? Look at the animal/plant density /unit volume of water in a tank vs. the ocean
Herefishyfishy
Skimmers are the most efficient means to keep up O2. Plunging water is another one but it will not out compete a good skimmer, unless you want to deal with salt sray everywhere. Air stones do work, they just are not as efficient as say a skimmer. When bubbles are generated and rise to the surface three things happen.
1. The formation of the bubble creates a micro-pressure around it, kinda like a mini O2 reactor, which drives O2 into the water.
2. As the bubble rises there is a gas exchange between the bubble and the water, due to diffusion, O2 out CO2 in. The smaller the bubble the more surface area/unit vol and the slower the rise, thus more gas exchange place.
3. As the bubble breaks at the surface it breaks the surface tension and causes water motion/agitation, thus the more O2.
steve-s
Error Bud
You can saturate water with all the O2 you want but if it has too much CO2, the pH won't budge. "the pH will crash"
O2 in the reef tank
I do not think for the most part it is a concern, as most tanks have acceptable levels. I have often stated and have bad debates about saturated O2 levels in reef tanks, in which case I argued they are usually not. People just assume it is saturated. And each time I ask, based on what measurements have you done, the thread seems to stop. Eric's article proves my point, that few tanks are 100 % saturated. I spent years playing with O2 measurements in FW and Seawater with a kit that test to .02 ppm O2.
There are only 2 kits out there that are worth a dam. The LaMotte, which tests to .1 ppm and one yon can afford and is good enough and the master for O2 kits, the HACH Digital Titrator for the tune of $200, that test to .02 ppm O2. Most cheap meters are useless, as they do not have adjustments or compensate for Salinity and Altitude.
If you are just wondering what is 100% saturation in your tank there is a std equation for this. You need to know your tank temp, salintiy and have a barometer
S¹= S x p¹/ 29.92 - ( C X F)
S¹= Solubility of O2 for Corrected Pressure
p¹= Barometeric Pressure (Barometer reading in inches)
S = Solubility of Distilled Water (from table, 8.2@25C & 7.9@28C)
C = Chorinity Reading of Sample (for us 18-20 ppt Chlorinity, std
seawater is 19=35 ppt Salinity)
F = Chorinity Factor, from table (for us it will always be .08)
or in old fashion where the two equations are not combined
S - ( C x F) = Corrected Solubility
S= Solubility of O2 in Distilled Water
C = Chlorinity reading
F = Factor for the difference per 1.0 ppt Chorinity
When dealing with altitude or changes in barometeric pressure we replace S with S¹, so
S¹ = S x ( p¹ / 29.92 )
S= Solubility of distilled water
p¹ = another barometric pressure other than std, which is 29.92 inches of Hg
If your tank is 82 F that will be about 6.4 ppm =100% Saturation
Roughly 35 ppt Salinity = 19 ppt Chlorinity
so 1 ppt Cl = 1.84 Salinity
http://www.sablesystems.com/baro-altitude.html
If you were dealing with a table for altitude @ 5800 ft.
pA¹ = 23. 99 (In. Hg. Abs.)
8.2 x (23.99/29.92) = 6.575
If your salinity was 1.021 or about 29 ppt, saturation for O2 @ 25 C would be
6.575 - ( 15.76 x .08) = **5.31 mg / l O2 with 1.021/29 ppt salinity
and if it was at NSW of 35 ppt/1.026 at the same altitude and temp
6.575 - ( 19 x .08) = **5.05 mg / l O2 with 1.026/35 ppt salinity.
It is best NOT to use altitude values but the above barometer values. Reason, the barometric pressure at say 1,000 ft is not always the same.
Or for lazy people
http://www.aquanic.org/images/tools/oxygen.htm
http://www.mrhall.org/science/oxygen/oxygen.htm
I was scrolling and hoping someone would post Eric's articles. Thanks Curt
I might add that is was a well done article by Eric.To be short
Don.
Pure O2 in a reactor is an absolute no-no. I would not worry about the redox but the O2 going to high. One would have to have an O2 monitor to run such a system to be safe. Second you do not need a reactor with pure O2. A reactor would make it worse, two-fold. 1. allot of mixing. 2. increasing the pressure just by itself increases O2. The higher the psi inside the reactor the more O2 is forced into the water. O3 does almost nothing for increasing O2, until all things are oxidized. Even then, often the O3 just remains O3. The reason behind degassing towers in some aquatic systems using O3. O2 / CO2 skimmer gas thing. You are partially right. It revolves more around the partial pressures of CO2 vs. O2, in water and in the air. They are very different.
Sara
What I'd like to know/understand is why the oxygen levels fall so much at night in tanks but not in the open ocean. In other words, this chart interests me:
For the same reason your pH goes up during the day and down during the night, due to CO2. "Plants" are giving off O2 during the day and consuming O2 at night.
Oceans ? Look at the animal/plant density /unit volume of water in a tank vs. the ocean
Herefishyfishy
Skimmers are the most efficient means to keep up O2. Plunging water is another one but it will not out compete a good skimmer, unless you want to deal with salt sray everywhere. Air stones do work, they just are not as efficient as say a skimmer. When bubbles are generated and rise to the surface three things happen.
1. The formation of the bubble creates a micro-pressure around it, kinda like a mini O2 reactor, which drives O2 into the water.
2. As the bubble rises there is a gas exchange between the bubble and the water, due to diffusion, O2 out CO2 in. The smaller the bubble the more surface area/unit vol and the slower the rise, thus more gas exchange place.
3. As the bubble breaks at the surface it breaks the surface tension and causes water motion/agitation, thus the more O2.
steve-s
Error Bud
You can saturate water with all the O2 you want but if it has too much CO2, the pH won't budge. "the pH will crash"
O2 in the reef tank
I do not think for the most part it is a concern, as most tanks have acceptable levels. I have often stated and have bad debates about saturated O2 levels in reef tanks, in which case I argued they are usually not. People just assume it is saturated. And each time I ask, based on what measurements have you done, the thread seems to stop. Eric's article proves my point, that few tanks are 100 % saturated. I spent years playing with O2 measurements in FW and Seawater with a kit that test to .02 ppm O2.
There are only 2 kits out there that are worth a dam. The LaMotte, which tests to .1 ppm and one yon can afford and is good enough and the master for O2 kits, the HACH Digital Titrator for the tune of $200, that test to .02 ppm O2. Most cheap meters are useless, as they do not have adjustments or compensate for Salinity and Altitude.
If you are just wondering what is 100% saturation in your tank there is a std equation for this. You need to know your tank temp, salintiy and have a barometer
S¹= S x p¹/ 29.92 - ( C X F)
S¹= Solubility of O2 for Corrected Pressure
p¹= Barometeric Pressure (Barometer reading in inches)
S = Solubility of Distilled Water (from table, 8.2@25C & 7.9@28C)
C = Chorinity Reading of Sample (for us 18-20 ppt Chlorinity, std
seawater is 19=35 ppt Salinity)
F = Chorinity Factor, from table (for us it will always be .08)
or in old fashion where the two equations are not combined
S - ( C x F) = Corrected Solubility
S= Solubility of O2 in Distilled Water
C = Chlorinity reading
F = Factor for the difference per 1.0 ppt Chorinity
When dealing with altitude or changes in barometeric pressure we replace S with S¹, so
S¹ = S x ( p¹ / 29.92 )
S= Solubility of distilled water
p¹ = another barometric pressure other than std, which is 29.92 inches of Hg
If your tank is 82 F that will be about 6.4 ppm =100% Saturation
Roughly 35 ppt Salinity = 19 ppt Chlorinity
so 1 ppt Cl = 1.84 Salinity
http://www.sablesystems.com/baro-altitude.html
If you were dealing with a table for altitude @ 5800 ft.
pA¹ = 23. 99 (In. Hg. Abs.)
8.2 x (23.99/29.92) = 6.575
If your salinity was 1.021 or about 29 ppt, saturation for O2 @ 25 C would be
6.575 - ( 15.76 x .08) = **5.31 mg / l O2 with 1.021/29 ppt salinity
and if it was at NSW of 35 ppt/1.026 at the same altitude and temp
6.575 - ( 19 x .08) = **5.05 mg / l O2 with 1.026/35 ppt salinity.
It is best NOT to use altitude values but the above barometer values. Reason, the barometric pressure at say 1,000 ft is not always the same.
Or for lazy people
http://www.aquanic.org/images/tools/oxygen.htm
http://www.mrhall.org/science/oxygen/oxygen.htm
Last edited:
Boomer
Well-known member
Damn, looks like I scared everybody away again
Curtswearing
Mantisfreak
Damn, looks like I scared everybody away again
Not until you got to the corrected pressure equations. Yikes!!!
Scooterman
Well-known member
Originally Posted by Boomer
Damn, looks like I scared everybody away again
Not until you got to the corrected pressure equations. Yikes!!!
Yep I was good until that point, leave it to Boomer
Boomer
Well-known member
Pretend they are not there and use the calculators on the links But guys, they where just simple multiply, divide and subtract
But guys, they where just simple multiply, divide and subtract
Curtswearing
Mantisfreak
Oh, I can do the math. I'm just one of the lazy guys!!!
Herefishyfishy
Smart Bass
Not scared away, just had everything in the entire universe about oxygen solubility in an aquaria explained in one post! (thanks, it did really help)
(thanks, it did really help)
Boomer
Well-known member
OK, we are good then
Maybe that's part of the confusion... in the IMAC video he does specifically talk about macro too.
I agree with Boomer that it's a great article. So maybe we should just stick to that and not think too much about the lectures. lol
Maxx
Staff Housemonkey
- Joined
- Jul 31, 2003
- Messages
- 2,935
Boomer,
Its interesting to me that Eric specifically stated Skimmers are not very good oxygenating the water. I would assume that the type of skimmer involved would have alot to do with how well it oxygenated as well.
When Eric made that statement, my first thought was the slow flow through rates reccomended for recirc skimmers.
Does flow through rate of the skimmer affect how well it oxygenates the water column?
Nick
Its interesting to me that Eric specifically stated Skimmers are not very good oxygenating the water. I would assume that the type of skimmer involved would have alot to do with how well it oxygenated as well.
When Eric made that statement, my first thought was the slow flow through rates reccomended for recirc skimmers.
Does flow through rate of the skimmer affect how well it oxygenates the water column?
Nick
I know this much... oxygenation (via aeration) depends on the contact time between the air and the water. It's the same for any gas I believe. I remember when I had one of the cheaper CO2 injectors for one of my planted freshwater tanks, that was the point of the "bubble ladder." The longer the bubble stayed submerged, the more gas got dissolved.
Scooterman
Well-known member
Nick I would have a hard time thinking the skimmer isn't as good as an oxygenator as any, If anything I'd think it is a great at oxygenating, unless it is sucking in air from a polluted source maybe?
