ph control with oxygen
- Thread starter Art2249
- Start date
- Tagged users None
So I'm a little confused. people sometimes run their skimmer intake to the outside in order to reduce the amount of CO2. Supposedly this helps raise the PH somewhat. Wouldn't injecting O2 into your skimmer accomplish the same thing. I will say that when I aerated fresh saltwater with oxygen vs. an air pump the PH was higher. I actually had to switch over to room air for couple hours before using it.
Xclusive Reef
Valuable Member
- Joined
- Sep 26, 2016
- Messages
- 1,591
- Reaction score
- 852
you are correct. I also run a hose from outside to my skimmer and raises ph slightly. Using O2 would cost a lot if you were thinking bout using a tank.. cheaper to pull air from outside.
Velcro
2500 Club Member
Pulling outside air into the skimmer raises pH because it had less co2 than indoor air. Sure, oxygen fed to a shimmer intake would have less co2 as well, but you're talking about a huge amount of air that would deplete the oxygen tank relatively quickly.
So I guess what's happening is your not trying to raise ph with oxygen rather you are preventing CO2 from lowering ph by displacing it. I have a used O2 concentrator from a yard sale. It pulls 3 amps. You can adjust it from 1 to 5 liter/min. I wonder if you Could program the controller to operate it?
Velcro
2500 Club Member
I don't think oxygen concentraters remove co2 from the air that they use. I think they only remove nitrogen.
No actually I use oxygen at night because of sleep apnea. It bleeds into my cpap at 2 lpm. The machine produces about 96% pure oxygen. I bought the one from a yard sale as a backup it was $100. The one I use for sleep has been running every night for 3 years. its about halfway through it's lifetime.
chipmunkofdoom2
Always Making Something
Oxygen has absolutely no effect on pH in reef aquaria. The reason that drawing outside air into your skimmer raises your pH has nothing to do with oxygen. It is because the air from outside has less CO2 in it than the air in your home. If you see an increase in pH by forcing 100% oxygen into the tank, it is because there is no CO2 in the pure oxygen and all of the oxygen you are dissolving in your tank is displacing some of the CO2 in the water. The oxygen is not raising the pH directly. Note that air is made up of much more than just oxygen: replacing all the other natural atomspheric gasses in your tank with only oxygen may cause harm to the animals in your tank.
Please read Randy's article on low pH to get a better idea of how pH works in reef aquaria. pH in reef aquaria is controlled in part by carbonate alkalinity and in part by dissolved CO2. It is not controlled by dissolved oxygen.
Please read Randy's article on low pH to get a better idea of how pH works in reef aquaria. pH in reef aquaria is controlled in part by carbonate alkalinity and in part by dissolved CO2. It is not controlled by dissolved oxygen.
Yea I would think 100% definately be bad. But what if you only raised O2 by a fraction? Say 25% vs 21% ? So let's say you have a large skimmer How much air does it pull? What would be the effect of injecting 1/2 lpm O2?
chipmunkofdoom2
Always Making Something
This is a very difficult question to answer, but the answer is likely not relevant in the context of increasing pH in seawater. Randy might be better able to answer this one.
I can say that oxygen and carbon dioxide are not foils in seawater with regards to pH. In other words, if CO2 is bad for pH, oxygen is not necessarily good. pH in seawater is controlled by a very specific balancing of carbonate, bicarbonate and carbonic acid. Assuming constant carbonate alkalinity, CO2 decreases pH, while absence of CO2 increases it. It is only by adding or removing CO2 from seawater that we can push the equilibrium one direction or another, and thereby affect pH.
Well I appreciate the discussion anyway. Thanks for the info. here is my tank build if you're interested. https://www.reef2reef.com/threads/art2249s-160g-build.383321/
Brew12
Electrical Gru
This is actually a fairly easy question to approximate.
CO2 makes up 0.04% of air. Your skimmer probably pulls around 10L per minute of air flow. Adding an additional 1/2L per minute of pure oxygen would displace around 5% of the total air. So, it would reduce the 0.04% by an additional 5%. Using this, you would reduce the total amount of CO2 added by 0.002%. In other words, you likely wouldn't notice.
Hope that helps!
Edit: Of course, I found a flaw in my logic. Even though it would reduce CO2 content by .002% (making it roughly 0.038% of the total injected volume) the actual reduction in CO2 in the water would still be 5%. My conclusion should still be right in that it would be negligible and would not create a 5% change in pH. This is due to the equilibrium equations impacting pH/Alkalinity and the fact pH is a logarithmic scale.
CO2 makes up 0.04% of air. Your skimmer probably pulls around 10L per minute of air flow. Adding an additional 1/2L per minute of pure oxygen would displace around 5% of the total air. So, it would reduce the 0.04% by an additional 5%. Using this, you would reduce the total amount of CO2 added by 0.002%. In other words, you likely wouldn't notice.
Hope that helps!
Edit: Of course, I found a flaw in my logic. Even though it would reduce CO2 content by .002% (making it roughly 0.038% of the total injected volume) the actual reduction in CO2 in the water would still be 5%. My conclusion should still be right in that it would be negligible and would not create a 5% change in pH. This is due to the equilibrium equations impacting pH/Alkalinity and the fact pH is a logarithmic scale.
Last edited:
Randy Holmes-Farley
Reef Chemist
Staff member
Super Moderator
Excellence Award
Expert Contributor
Article Contributor
R2R Research
My Tank Thread
Adding O2 won't alter pH. CO2 and O2 do not compete for "space" in the water. You can have any combination of one high and the other low, both high, both low, etc.
If you bubble O2 so strongly that it is bubbling out the top of the water, some CO2 gas will enter the O2 bubble and be swept away. That would tend to raise pH, but could be done with any gas (e.g., N2) just as well (from the pH perspective, anyway.).
If you bubble O2 so strongly that it is bubbling out the top of the water, some CO2 gas will enter the O2 bubble and be swept away. That would tend to raise pH, but could be done with any gas (e.g., N2) just as well (from the pH perspective, anyway.).
Randy Ruiz
Community Member
Doesn’t keeping the water surface moving affect dissolved oxygen? Does this affect pH?
Randy Ruiz
Community Member
Thanks
HuduVudu
2500 Club Member
For reference:
Things that make you go hmmm. If you are locked in a room with no means of ventilation, from what will you die?
- Nitrogen -- N2 -- 78.084%
- Oxygen -- O2 -- 20.9476%
- Argon -- Ar -- 0.934%
- Carbon Dioxide -- CO2 -- 0.0314%
Things that make you go hmmm. If you are locked in a room with no means of ventilation, from what will you die?
Brew12
Electrical Gru
Keeping surface water moving impacts the CO2 content in the water, which impacts pH.
Brew12
Electrical Gru
Boredom.
