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Selling at $850 with reagents. No box. Still under warranty. Collect at CCK

nice post! followed your advise and waiting for your next post

Kh Measurements - Alternative I end up getting a kH monitor. The device does not use reagents, does not produce waste liquid, does not require frequent calibrations. Too good to be true? In most cases, it would be. But thanks to good science and clever engineering, there is a solid alternative for kH monitoring. kH measurements (Part II) Other than titration method, there is another way for us to determine the carbonate hardness of the aquarium. For a carbonate buffer, such as seawater, the kH, CO2 concentration and pH are correlated. This means, if we know the pH of the aquarium, as well as the concentration of CO2 in the water, we can reliably calculate the kH of the water. You can take a glance at this article. Such measurements is not without its challenges. Firstly, in order for the kH calculations to be accutate, the pH measurements must be very accurate and precise. This requires properly calibrated pH probes which is accurate to 0.01 pH. Probes which can do this with consistency are generally very expensive. Not to mention frequent calibration is needed. Secondly, measuring of carbon dioxide concentration in water is expensive and inaccurate. Therefore if we want to measure the kH in this way, we have to solve two expensive problems: accurate measurement of absolute pH and CO2 concentration. Engineering to the Rescue Fortunately. There are ways to bypass these costly problems. If we can't measure the CO2 concentration in the water, can we adjust the sample to a known value? Turns out we can. By bubbling the sample water, we can make the CO2 level in the water to be the same as the air around it. Measuring CO2 concentration of air is easy and cheap. This, however, means we still need to have an extremely accurate pH probe, as well as a (cheap) meter to measure CO2 level. Again, engineering to the rescue. An Elegant Solution If we have two samples of water, at the same temperature, same CO2 concentration. Then the difference in kH is only affected by the difference of the pH of the liquids. And if we bubble two liquids with the same air. They will have the same CO2 concentration. If we use the same pH probe to measure the pH of both solutions, then the difference in pH can be measured very accuratly. [ for example, two liquids at pH of 8.01 and 8.03 respectively. The difference in pH is 0.02. If a pH probe is not well calibrated, it may read 7.99 and 8.01. The difference is still the same] This neat trick completely bypass the need to accurately measure any CO2 level, or having to measure the absolute pH. Oh wait. There is more icing on the cake. Since nothing (except air) is added into the sample, the water can be return unchanged to the aquarium. In addition, since it's not based on titration, the sample volume does not matter at all, which means there is no need to calibrate the sample pumps at all. All in all, in my opinion, too good but true. AquaWiz The device is AquaWiz. I have been using it for more than 2 month. It runs very well for me. I'll write more about it in the next post.