Reefs.org Forums

[wade]

Sorry, didn't see anywhere else to put this.

I have some serious concerns regarding the assumptions made and voiced in Mr Jordan's article concerning air quality. Its well understood that CO2 concentrations in the water can affect pH in aquatic systems. However, the work he did (basically just sitting in a room monitoring levels) really doesn't mean anything. There were no replicates, no validation, and no references. It sounds more like an article written by someone with only mild understanding.

My real concern is that people will take the article at face value and not question its contents. The real factor affecting pH in a closed system, especially in a well established system, is more likely to be its occupants. While atomspheric concentrations of gases have a role, that role is moderated by exchange, saturation, and buffering capacity. None of those items are strongly mentioned nor considered.

In order to make the assumptions made in this context, he would have had to use a control tank (one with outside air source) and an exposure tank (indoor/high CO2 source) that had no photosynthesizing animals in them. In order to validate the points, replication would be needed.

I hope that my concerns don't seem outlandish or overly critical, but I don't want people coming away with the thought that bringing in outside air is an answer to pH problems in and of itself. As well, air quality is extremely variable depending on where you live and certain areas would be more detrimental to a tank.

Thanks,
Wade

[AF Founder]

Wade,

Your points are certainly well taken, but keep in mind that this "Short Take" was a modest little piece, dealing simply with the effect of atmospheric CO2 on tank pH. It never intended to deal with the variables you spoke of.
Many of us have noticed a significant pH drop when a lot of people were in a fish room to observe someone's reet tank.

[Randy Holmes-Farley]

FWIW, many people that have low pH problems have found them to be solved by opening a window. Obviously this isn't the answer for every situation, especially those where the low pH is caused internally by such things as CaCO3/CO2 reactors. Still, it has proven useful to many.

[Robert Jordan]

Wade,
Your concerns are duly noted. The article I wrote was just for only one of the many reasons pH drops too much overnight in well seal homes with not enough fresh air ventilation. There were many tests I performed with the carbon dioxide monitor and I quickly saw the relationship between the indoor concentration of 1200 ppm and a rapidly dropping pH. When the fishroom is ventilated well enough to match closely with the outdoor concentration, (about 340 ppm) I noticed very little change in pH overnight. As an aquarist and not a researcher, It would have been foolish of me to go to the expense of setting up an outside control tank to confirm my test results. The monitor was brand new and I have no reasons to doubt it's readout. This monitor is now in use continously and is the first thing I look at when pH seems lower then it should. In every case, when I allow more fresh air to enter the fishroom, the pH will start to rise even when photosynthesis stops and after enough carbon dioxide gets blown off by the skimmer. Bob Jordan.