low pH, fresh air, what the heck?

[salty joe]

My tank's pH is almost always below 7.8. The house is tight and we do a lot of cooking with gas so that makes sense.

The tank has a fairly tight fitting lid to limit evaporation and it works well. So, I am pumping fresh air from outside under the tank's lid. The volume of air between the water surface and bottom of lid is about equal to what the air pump delivers in 5 or 6 minutes. I started last night and the pH hasn't gone up at all. I went outside and checked the air inlet-it's definitely drawing air. I also checked the air outlets under the tank's lid. The supply line is 1/2" PVC all glued, I'm confident there are no leaks. The water's surface is swirling and turbulent. I floated Styrofoam in the sump/fuge to prevent CO2 from getting in there.

I'm using a new BRS double junction pH probe. Alk is about 7.6.

Could it be that it will take a few days to see the pH go up?

 

[Randy Holmes-Farley]

My tank's pH is almost always below 7.8. The house is tight and we do a lot of cooking with gas so that makes sense.

The tank has a fairly tight fitting lid to limit evaporation and it works well. So, I am pumping fresh air from outside under the tank's lid. The volume of air between the water surface and bottom of lid is about equal to what the air pump delivers in 5 or 6 minutes. I started last night and the pH hasn't gone up at all. I went outside and checked the air inlet-it's definitely drawing air. I also checked the air outlets under the tank's lid. The supply line is 1/2" PVC all glued, I'm confident there are no leaks. The water's surface is swirling and turbulent. I floated Styrofoam in the sump/fuge to prevent CO2 from getting in there.

I'm using a new BRS double junction pH probe. Alk is about 7.6.

Could it be that it will take a few days to see the pH go up?

Do you have a skimmer and what air is it getting?

 

[GoVols]

Do you have a skimmer and what air is it getting?

Really good question.

I lift all my windows at times to get as much trapped in Co2 out.

@salty joe
Have you tried taking some of your tanks display water outside with a bubble'r and see if it's ph rises in a hour?

 

[salty joe]

I don't have a skimmer-just an algae scrubber.

Great idea to take some water outside and bubble it! I'll do it first thing tomorrow.

 

[Jason mack]

I found that raising my alk to around 8.0.- 8.3 dkh helped raise my ph ..

 

[siggy]

moved

 

[salty joe]

I found that raising my alk to around 8.0.- 8.3 dkh helped raise my ph ..

How much did that raise pH? Where was your alk to begin with?

I bubbled a glass of water outside for a little over an hour and the pH went from 7.75 to 7.93. I also bubbled a glass of water in my fishroom using the air I'm trying to raise pH with and it went up to 7.98. (there was more air with the fishroom test)

I'm at a loss for why blowing fresh air across the surface hasn't dented the pH in a day.

 

[Jason mack]

How much did that raise pH? Where was your alk to begin with?

I bubbled a glass of water outside for a little over an hour and the pH went from 7.75 to 7.93. I also bubbled a glass of water in my fishroom using the air I'm trying to raise pH with and it went up to 7.98. (there was more air with the fishroom test)

I'm at a loss for why blowing fresh air across the surface hasn't dented the pH in a day.

If I keep my alk at 8.3-8.6 dkh then my ph stays above 8.0 -8.2

 

[Randy Holmes-Farley]

How much did that raise pH? Where was your alk to begin with?

I'm at a loss for why blowing fresh air across the surface hasn't dented the pH in a day.

The additives you use to boost alkalinity will have some impact on pH until it re-equilibrates with the air, but the boost from 7 dKH to 8.5 dKH will boost seawater in equilibrium with air (any air) by about 0.08 pH units.

If it only went to 7.93 outside, then your pH calibration may be a bit low.

Also, the thome air is not the only source of CO2. The tank itself is, and if aeration is not complete, the tank pH can be lower than equilibration with the air would suggest.

 

[don_chuwish]

Giving a skimmer outside air (or CO2 scrubbed air) would certainly do more than just fresh air across the top. Also, floating that styro is going to be more harm than good. CO2 needs to escape.

 

[salty joe]

I thought I had this figured out-the air pump gets pretty warm. If the fresh pumped air is warmer than the air under the lid, maybe the pumped air is riding or floating along the lid and hardly contacting the water. The pumped air is 3 degrees cooler. So much for that idea.

Giving a skimmer outside air (or CO2 scrubbed air) would certainly do more than just fresh air across the top. Also, floating that styro is going to be more harm than good. CO2 needs to escape.

I floated the Stryro with the assumption that there's enough CO2 in the air to drop my tank's pH and fresh air over the tank would drive out CO2. At that point, CO2 would enter the sump's surface water unless it was covered. That was the plan anyway. I don't have a skimmer.

The additives you use to boost alkalinity will have some impact on pH until it re-equilibrates with the air, but the boost from 7 dKH to 8.5 dKH will boost seawater in equilibrium with air (any air) by about 0.08 pH units.

If it only went to 7.93 outside, then your pH calibration may be a bit low.

Also, the thome air is not the only source of CO2. The tank itself is, and if aeration is not complete, the tank pH can be lower than equilibration with the air would suggest.

If it matters, I don't have an air stone. I just put the air hose in water for the de-gas tests and got 7.98 on the fish room test.

I calibrated the probe less than a week ago but double checking is good. It was a little off. Now my pH reads 7.73, before it read 7.75. Ugg.

Just checked alk and it's 7.3. My target for alk has been 8, maybe I should shoot for 9.

I recently added enough kalk to raise calcium from 400 to 420 and the pH bumped up to 7.85 and stayed there for a couple days before creeping back down. Is it possible that after a few more days the fresh air blowing over the water will finally start to raise pH?

 

[Randy Holmes-Farley]

I thought I had this figured out-the air pump gets pretty warm. If the fresh pumped air is warmer than the air under the lid, maybe the pumped air is riding or floating along the lid and hardly contacting the water. The pumped air is 3 degrees cooler. So much for that idea.



I floated the Stryro with the assumption that there's enough CO2 in the air to drop my tank's pH and fresh air over the tank would drive out CO2. At that point, CO2 would enter the sump's surface water unless it was covered. That was the plan anyway. I don't have a skimmer.





If it matters, I don't have an air stone. I just put the air hose in water for the de-gas tests and got 7.98 on the fish room test.

I calibrated the probe less than a week ago but double checking is good. It was a little off. Now my pH reads 7.73, before it read 7.75. Ugg.

Just checked alk and it's 7.3. My target for alk has been 8, maybe I should shoot for 9.

I recently added enough kalk to raise calcium from 400 to 420 and the pH bumped up to 7.85 and stayed there for a couple days before creeping back down. Is it possible that after a few more days the fresh air blowing over the water will finally start to raise pH?

Generally the effect of fresh air should be apparent after a day.

If you do not see higher pH with outside air aerating a cup of water, compared inside air, the outside air won't alter the tank pH. ALso, if the tank pH is well below the pH of water aerated inside, then the tank needs more aeration (with either indoor or outdoor air).

 

[Jwheld]

Have you tried CO2 scrubbing the air for the bubbler? You can make fairly simple canisters to test to see what the tank pH does. This may take the guess work out of where CO2 is coming from and how it's affecting your tank.

 

[salty joe]

I bubbled the fresh air counter current in 2" PVC and got a good pH bump of over 0.1. I also raised alk a little and replaced what little evaporates with kalkwasser. Now, pH stays above 8.0, a huge difference. I also ended up with an old school counter current skimmer that pulls out a fair amount of goo using very little energy.

I still don't get why fresh air across the surface didn't help because the surface is where CO2 gets in the tank.
Anyway, thanks you guys for kicking this around with me.

 

[salty joe]

sorry double post

 

[Randy Holmes-Farley]

I still don't get why fresh air across the surface didn't help because the surface is where CO2 gets in the tank.
Anyway, thanks you guys for kicking this around with me.

CO2 is also made in the tank by respiration. That's a main reason why pH swings day to night..

Glad to hear it helps.