Oliver,

Thanks again for this valuable information
delivered so painlessly and generously.
You have mentioned several times
the importance of knowing the level of Dissolved O2 in our water
versus the expense of a meter to measure DO2.

I just ran into this Tetra Oxygen (O2) Test Kit;
for less than $20 ($12.99 at petsandponds.com)
one receives reagents and instructions for thirty tests,
said to be accurate for DO levels from 2-14mg / L.
(Since one mg is one millionth of a litre,
for all practical purposes 1 mg/l of DO = 1ppm DO)

What do you think of these test kits,
and have you had particularly good results/reports
on any specific brand?