[farne230]

Quote: Originally Posted by koibooi KH is Total Alkalinity or Carbonate Hardness and is a measure of the buffering capacity of the water in the pond. The buffering capacity refers to how well the pond can resist changed in pH. As I understand, the minimum KH should not be below 4 degrees of hardness and the ideal is between 6 degrees and 8 degrees. I must say that I do not quite understand this "buffering" business. I have however never been successfull in actually measuring my KH. the NT Labs test kit say that you must add one drop of solution to the water sample and then the water turns pale blue. Then you must keep on adding drops until the blue turns to yellow. When ever I did the test, my water was yellow from the start so I have never managed to actually measure KH. I do have a 2 meter long by 300 mm wide by 300 mm deep tray in my trickle tower which is filled with oyster shells so my pH is always stable.

I had the same problem, went back to the pet store and replace the KH bottom twice. This was a red sea product, but this could happen to any of them. I switched brands and the kh finally worked. I am using Pharmasudicals product, but the point is the experation dates and the products have a short half life. Purchase another bottle.