easy to calibrate. vinegar and baking soda in water have pretty constant pH.
also, soak shredded red cabbage in 50oC water for 1/2 hour makes pretty good pH
solution. http://weloveteaching.com/0spring/0l...lab-water.html

Ingrid

On Mon, 20 Apr 2009 01:46:57 EDT, ~ jan wrote:
http://www.hammockkoifarm.com/koi-care-products.html
Is the salt meter I use. I see they have a pH meter, I thought those had to
be calibrated? Hmm..... ~ jan