HumblePie
Lifer
Where did the initial Ammonia come from?
Tap Water - No
Gravel - No
Additives - Not likely
Contaminated water? - Cat Pee?
Cleaning agents left on inside of tank? - Could be that Petsmart cleaned the tank with Windex before they put it on display. Did you rinse the tank well before adding gravel and water?
HOB Filter? - You could have bought a returned filter with organic material in the guts from a previous owner.
You should probably scrub the tank, and wash the filter good and see if your Ammonia spikes again. If it does, then break it down and rinse everything. Start from scratch so the mystery Ammonia doesn't come back.
If Ammonia doesn't come back after scrubbing tank, then see if tank will cycle.
Not the cats peeing in it. Have a completely tight hood on it and I would see the pee residue, as well as smell it, if they had tried it.
The other suggestions about the windex and HOB make sense though. Petsmart stopped carrying extras of tanks in the back per store. They only have demo models. So if a demo is bought you have to wait for another to shipped to the store to pick it up. Which means the tank I bought was a floor model and was possibly contaminated with cleaning supplies. That was something I didn't think off and makes some sense. Although that wouldn't be that large of amount of ammonia residue left over I would think.
As for the returned HOB filter I purchased that could be the case as well. Picked up the emporer from Alamo Aquatics and not pet smart because they were cheaper. They only had one on the shelf and the place is a smaller mom & pop style store. While everything looked new, there is a good chance it could have been a cleaned up returned item.
As for now I'm going to leave it as is. I bought some Tetra Safe Start over lunch and added it in. Expensive stuff, but I was reading reviews and it's the only proven bottle of bacteria to work with published research, tests, and findings to back it up.