I'm just trying to pull together the router & 1wire stuff into an operational pile of parts at the moment, but I appreciate the work that's been done so far. This project definitely looks like it'll provide the control that I'm sure I'd need if I had a tank up and running...
First things first, eh?
Regarding the pH probe interface: anything I've learned about electronics vanished years ago when I turned to the Soft Side and away from the messy analog realm, but would it not be possible to throw a handful of diodes at the thing in order to split the negative and positive voltages into two separate A/D converter channels, while inverting the negative to produce a positive input?
I realize that it wouldn't be ideal, as you'd have the acidic side on one channel and the basic on the other, but you could recombine them in software and read the full range of the probe, after some amplification.
I'm sure there's a very fundamental reason why this wouldn't be possible, but I'll probably blow up my router and/or pH probe just to check things out. I find the pretty sparks enchanting...