I tested my tank today and got no ammonia/ammonium for the first time in almost a month and a half. I'm not sure what happened, but my bio filter was damaged somehow and I had an ammonia spike so I had to use ammolock to keep my fish alive. Then, I had nitrites starting to spike, so I added Amquel+ to get rid of that. Then I found out the amQuel+ is not compatible with any test kit I could find except the hang inside the tank ammonia monitor from Seachem. So, although that was reading that the free ammonia was pretty low to 0, I wasn't sure how accurate it was because my APO test was reading 8ppm of ammonia for over a month. For the last week my hang in the tank monitor has said 0 ammonia my API test was still reading around 4ppm. But, now it's all clear!! So, happy! Nitrites at 0 too.
Still not problem free yet though, I have camalanus worms to get rid of now.
Also, a swordtail I just bought from a LFS had popeye and died from it within hours of me seeing that it had the problem, so now I'm treating the tank for that now too just to make sure my other fish don't get it.
I think I have had every problem that you could possibly have, and in only a bout 3-4 months!
Still happy about my bio stats though.