Well .. I didn't forget about you peasly1.
Several things could have led to your rise in pH.
Ruling out the possibility that you added any excess pH buffer supplements that would have raised it significantly like baking soda, and you are not adding kalkwasser too fast, I will take swag at it.
You had 2 fish die in the tank. Sounds like one jumped out of the tank, the other still missing ?
Have you determined what was the cause of the other fish's death?
For the rise in pH - my guess is that you had 30 pounds of live rock in the tank - with a minimal amount of water circulation. Not much gas exchange at the surface of the tank, and poor circulation in the middle and lower parts of the tank.
Your pH was around 8.1 - 8.2 based upon your alkalinity (buffer) at the time, and your tank's oxygen O2 and carbon dioxide CO2 amounts were at some equilibrium under those conditions as well. You may have had poor gas exchange and a higher than desired level of CO2 in the water - but your pH was stable under those conditions.
It's possible - that by removing half of the live rock, you may have allowed what little water circulation you had to increase - allowing more CO2 and O2 gas exchange - CO2 and O2 concentration levels changed - and may have resulted in a swing in pH.
The pH of water is influenced by these changing concentrations of CO2. Carbon dioxide reacts with water to form carbonic acid. Increases in carbonic acid will drive your pH DOWN - but the chemical reaction goes both ways. A decrease in CO2 in solution will lead to a rise in pH.
Somewhat similar to the natural pH swings you see in a tank with fish and algae, as you go from day to night and back.
This may have been the cause - not sure - but it's one possibilty.
Sorry for the long reply - you asked what time it is and I end up telling how to build your own wrist watch <img src="graemlins//uhuh.gif" border="0" alt="[U-Huh]" />
Brian
