daviesri;11087 said:
With a pH of 6.9 and KH of 9.0 it looks like my fish should be stressing since CO2 should be 33.991. Yet they all look very content swimming at all levels of the tank. I am measuring the CO2 with a Milwaukee ph 600 meter and KH with an Aquarium Pharmaceuticals test kit. I also checked both with one of the strips and got pretty much the same readings. How does one reduce the KH?
I think we have all gone thru this experience. We measure KH and pH and the charts say we have, as in my case, 120 ppm of CO2, so we carefully watch the fish, but are afraid to add more or even leave it so high as it is. But, it cannot possibly be that high. The explanation is that the KH/pH/CO2 equation that is used to generate those tables only works if the water contains no source of alkalinity other than carbonates and no other source of acidity other than carbonic acid. And, our aquarium water rarely fits that specification. That means we just can't determine the ppm of CO2 using those charts.
Using the "drop checker" device eliminates that problem, by using distilled water, which has no source of alkalinity or acidity in it, and adding just sodium bicarbonate to gain a KH or 4 degrees. Then we establlish an equillibrium state between that water and the water in the tank so both have the same ppm of CO2 - that is done by the air gap connecting the two masses of water. Now, when we measure the pH of the water in the "drop checker", done with the indicator solution in it, we can use the KH/pH/CO2 table to accurately find how much CO2 is in that water, which is the same as is in the tank water. We can do it accurately, because the indicator is clearly green when it is green, and green means pH of 6.6, which gives 30 ppm of CO2 when the water KH is 4 degrees. I figure the margin of error for the 30 ppm reading is from 25 to 40 ppm, which is very good for such a measurement.
The problem with just slowly increasing CO2 bubble rate is that you have to be alert to signs the fish are distressed, the fish can become acclimated to higher than normal ppm of CO2 when you slowly increase it, and if you start doing this with a very low ppm of CO2 you can easily interpret normal fish behavior as a sign of distress and stop way before getting enouth CO2 in the water. I say this because I have done all of thes things. I lost a large group of my fish once by not watchng them carefully enough. I stayed at a very low ppm of CO2 once when I was just sure I had too much CO2, so I imagined some signs of distress. Then, when I finally got the drop checker working, and its color was yellow - meaning 70+ ppm of CO2, I laughed but looked at the fish, and all of them were gasping at the water surface. I dropped the bubble rate very quickly, and shut off the CO2 so the ppm would drop. I was just lucky not to lose more fish.
Sorry for being so long winded. It is only because I am very sold on the "drop checker" method for keeping track of the CO2.
