I know when I test my tanks I get 0 or non detectable on Ammonia and Nitrite. I do get reading for Nitrate just before a water change of 5-20 occasionally. Since removing most of my sponges I rarely even get that anymore.
I think your tank is going through a mini cycle - any dead fish that you didn't get out?
Anyway water change and really clean your filter media. FWIW I would only use a cannister filter to run carbon and let your live rock do the rest.
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