Ph correlation to nitrates

[lilbitreefer]

Going to be honest I havent been checking parameters like I should. I have a apex system and have just been going off of those values. For some reason my tank hangs out in thepH range of 7.6-7.7. Checked my nitrates and they are above 50 ppm. My phosphate test kit is gone and I am waiting for a replacement. My tank has been up for almost 2 years now and I have been poorly maintaining my zeovit system. As a fix to get my tank back into alignemnt I am doing water changes.

What could be causing my pH to be so low? Even when the parameters were on target the pH was always still low. I only have a hangful of corals. 2 leathers, 1 SPS, 1 anenome, and a bunch of mushrooms. They all seem fine right now, but polyo extension is minimal for the SPS.

 

[TomW]

I hesitate to put fingers to keyboard in Randy's forum, but the primary drivers - other things nominal - of pH in a reef tank are carbonate alkalinity and 'excess' dissolved atmospheric CO2, the former pushing pH up and the latter pulling it down. Frequently the culprit in reef tanks is high CO2 levels in our homes, way above the nominal 400ppm of outside air. Search Randy's archives; he's covered this pretty extensively over the years.

--Tom

 

[Randy Holmes-Farley Verified Community Expert]

Quite right.

pH is determined mathematically by the alkalinity and the CO2 level in the water. Nitrate does not have anything to do with it, at least not directly.

Low pH is quite common, and is usually due to elevated CO2 levels in closed up homes.

This has more:

pH And The Reef Aquarium
http://www.reefedition.com/ph-and-the-reef-aquarium/

 

[lilbitreefer]

The crappy thing about it is that I have aired out my house what the central air wasn't needed for that day and did not see much of a change. I understand the basics of the acidification process, I guess I was hoping there might be a third cause since I thought I already dealt with those factors. Thanks for the help.

 

[Randy Holmes-Farley Verified Community Expert]

The crappy thing about it is that I have aired out my house what the central air wasn't needed for that day and did not see much of a change. I understand the basics of the acidification process, I guess I was hoping there might be a third cause since I thought I already dealt with those factors. Thanks for the help.

Third cause could be measurement error.

 

[TomW]

1) It's quite striking how fast the CO2 in a closed house can rise. Being a nerd by nature, and frustrated by my own pH problems, I got a desktop CO2 meter (co2meter.com) and put it near the tank. If I stand in front of the meter, I can watch the levels rise due to my exhalation. Cooking on my gas cooktop can send it to 800 or higher in a few minutes.

2) In my experiments-of-opportunity, it takes several days of open windows to have the full effect on the tank's pH. The gas exchange - even with a skimmer and lots of surface turbulence - seems to have it's own time constants.

3) It's been interesting to log CO2 along with alk measurements.

--Tom

 

[Randy Holmes-Farley Verified Community Expert]

2) In my experiments-of-opportunity, it takes several days of open windows to have the full effect on the tank's pH. The gas exchange - even with a skimmer and lots of surface turbulence - seems to have it's own time constants.

--Tom

FWIW, CO2 is actually harder (slower) to equilibrate than other gases such as O2. The reason is that nearly all of the "CO2" in seawater is present as H2CO3/HCO3-/CO3--, rather than as an individual CO2 molecule, and it actually is a slowish process for the hydration step to happen in either direction:

CO2 + H2O <---> H2CO3

The half time for this reaction can be significant (seconds) so in each pass through a skimmer, the amount of CO2 added or removed may be far from equilibrium with the air.

 

[lilbitreefer]

An interesting thing I also thought about was while I was in Panama at the STRI there was a phd student expereimenting on ocean acidification and how it related to corals. Wouldn't it be interesting find that in cities that are so polluted with CO2 by opening the window there may not be much of a change due to the high c02 levels in the city compared to inside the house. This was just an interesting FYI.