Is this even possible?

[Boomsloth]

So the past weekend I went home to help my mom with moving to a new house. I also picked up my magnum 350 filter. I made a spray bar and new intake for it because it was going to replace the filter I already had in my 20g long. The tank was cycled before I left but the filter was not enough for the juvies i'm growing out in it. The plan was to have both filters running until the new one established a new colony of bacteria. unfortunately the power went out and the filter I had running dried out causing a huge ammonia spike. after many water changes to get the ammonia under .25, I set up the new filter and planned on just doing water changes for the next 4 weeks but after about a week it seems like its already cycled. is this possible?
Water test last night
ammonia 0 ppm
nitrites under 0.25ppm
nitrates 5 ppm

I've tested the tap and its not that. I retested today and its still consistent and nitrates went up a little.

 

[auntiejude]

The good bacteria live on all the surfaces in your tank - ornaments, substrate, and even the glass. So its possible that this has sped up the colonisation in your new filter.
Keep checking your water quality, do water changes as needed.