Thank you for the offer, Tom. But, I am out of ideas to try, so I don't really have a need for any better KH reference solution for now. This last one I made was the easiest to make, reacted about ten times as fast as the original ADA style glass device, and cost almost nothing - a piece of acrylic plastic sheet, a nylon screw, an O-ring, a suction cup airline holder, and a Tyvek Priority Mail envelope.

I suppose I will eventually want to experiment with my pH probe, but for now I am going to try to get my aquarium to looking decent again. But, of course, tomorrow is another day!

Well, 1000% faster response time is nothing to sniff at.
Cost is not much.

2 hours vs 20-30min.

Regards,
Tom Barr