Thanks for the replies... I should mention that I did not do anything
to the biowheel on the filter... that's where most of the bugs live,
right?

I also have plenty of gravel with all kinds of bio material in it, I
did a pretty good vacuuming with the recent change, though.

The update is there was a bit of a minicycle regardless... nitrites
went to .25, nitrates remained at 40. I removed the media cartidge
containing activated charcoal and replaced it with nitra-zorb
("downstream" of the main filter). I salted a bit more, but I think
I'm going to steer away from meds for now. Anyone used nitra-zorb
before? This is my first try.

I do have biozyme left over from setting up this tank a year or so ago.
Should I add that to stimulate some growth? Once again, I want to
clarify that I replaced the main filter cartridge and the charcoal
media in the Emperor, and didn't touch the biowheel. Am I not supposed
to change the filter cartridge every 4 weeks?

Thanks again!