alexanderM

I apologize if this has been asked already, but I did a search and couldn’t find the answer to my question. I read the following regarding the use of the CO2 table for estimating CO2;

“This calculator (and the chart based on this formula) will only work if your water is carbonate buffered. If your water contains high levels of phosphates, it will alter your water properties, and invalidate these CO2 calculations”
http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

My question is this…what constitutes high levels of phosphates? Does the regular dosing of phosphorus make these calculations invalid?

brad

I hope not. I think it has to do with ph altering products. Many adjust the ph by phosphorus. It`s just to caution that adding chemical ph adjusters don`t increase the amount of co2 in your tank.

Some tap water has high amounts of phosphate too. The small aditions we make for our plants isn`t going to throw the chart off.

alexanderM

would it be wise to include a margin of error upward or downward? in-other-words, assuming that the amout of phosphorus we dose does have a "little" impact...would this impact give us a reading that is falsely high in CO2 or low?

bharada

I think the issue with phosphates is if it is introduced by way of a phosphoric acid-based buffering solution. The pH charts are derived by calculating the relationship between the carbonate content vs. the carbonic acid produced by the CO2 injection. If you introduce another source of acid (phosphoric, or hummic for instance) then the pH reading will be affected by that acid content, rendering the KH-CO2 relationship invalid.