I checked the Ph of the RO-DI. It is not extremly high but I am seeing a
difference when I checked it between the probe and test kit readings. The
probe is reading 7.7 while the test kit shows 8.2. Odd they would both show
a much closer,but higher reading in the tank water. I will be buying a new
test kit and also following the recommended calibration steps for the probe,
outlined in the previous post, before I attempt to change anything else.
Thanks for the assistance offered so far.
Dave
"Robert Cadieux" wrote in message
...

"David Young" wrote in message
news:zPUhd.346600$MQ5.261894@attbi_s52...
Marc,
Nope, no additives. Auto water top off system of RO-DI. Salt levels
adjusted
as necessary.

Try checking your RO/DI water. DI resins are called "mixed" resins. One
resin replaces all cations such as Ca2+ and Na+ with acidic H+. The other
replaces anions such as Cl- with alkaline OH-. In a balanced resin the H+
and OH- neutralise each other instantly to form water. However resins can
become unbalanced for various reasons. The efficiency goes down and the
PH
swings one way or the other. The PH from your DI resin water could be
high
and has basically destroyed your tanks buffering capacity over time.

The way we can tell when a resin has gone bad in an industrial setting is
because the water smells fishy. Of course that doesn't work with an
aquarium :-)

Robert