Hey Galabar and face,
I ran some tests as you guys suggested. Here's what I found...
Test 1 - Tap water and Prime = 0 nitrite and 0 ammonia
Test 2 - Tap water, Prime, and Fritzzyme 7 = 0 nitrite and 0.5ppm ammonia
Test 3 - Tap water, Prime, Fritzzyme 7, and Dr. Tim's Ammonium Chloride = 0 nitrite and 4ppm ammonia.
Seems like the Fritzzyme is dead and producing ammonia. The Dr. Tim's may also be more potent than labeled.
(I started with 1 gal water and dosed each add-in accordingly.)
So, I think I dumped a ton of ammonia into my tank when I added the dying Fritzzyme. That must have caused the initial spike. I guess I've been fighting that ever since. Adding the Dr. Tim's ammonium chloride just exacerbated it.
And, as Lonkley pointed out, the nitrite-eating bacteria grow more slowly. So, here I am.
I guess the good news is I have a head-start on the ammonia-eating bacteria. ;)
Gonna do another massive water change and see where that gets me..