Hi David,
I've noticed the galvanic isolation issue on the Apex site and am looking into isolating the systems.
I looked at the Apex price for basic entry and saw $499 at a store in CO.
That is a pretty good price. I believe that was without probes.
Could you let me know if that is about right. (That's a pretty small system and maybe not what you work with.)

I think I could set up a temperature and water level monitoring system to watch a single tank for $199. My system uses the client's existing email address and a pre-existing computer and ISP. I guess that would be a cost too if the client didn't have one. The system could be expanded based on that for relatively little added cost. pH and conductivity probes start to jack up the price and increase the maintenance.
That reminds me.
Do you service your own probes or does Apex calibrate pH and conductivity sensors. (Sorry, I've forgotten if you monitor these.)
Please disregard this question if you don't.
Thanks again for the link to the manual. Interesting stuff.