One other thing. I should have illustrated the higher pH for you. A
total reading of 3, at a temp of 72F uses a factor of 0.0179 at a pH of
7.6. That would give you a reading of 0.0537, which is not "safe". So
you can see that fairly subtle changes in this relationship can nearly
eliminate most of the toxic form, or make it higher.

Like I said, any ammonia is bad. I'll bet that the fish don't really
care about the difference betwee 0.04 and 0.05, they just know it's
nasty. ;-)