[Pavel Chaloupka]

I completely agree with your statement Bernd, fish do not mind wether its 5.1 or 5.5 at least in most cases. For most species there is a safe range where eggs develop just fine. I was just talking about the case where the value shown by the pH meter would be under 6 and in fact in my particular case was 6 and a little higher which could even work for Paros, but would not work for other species I have. I also use my pH meter a lot as I prepare a lot of different types of water and some cultivation solutions for algae. I think it also depends on the type of electrode and type of device. I used to have very precise laboratory type devices couple years ago and I think the calibration lasted much longer, but I have obtained normal type stuff after it got old for the very exact reason you are mentioning. It realy does not matter if the pH is little higher or lower as long as you are within the range needed.