Ok lets hope I get answers to all your questions! My tap water tests and 0.5ppm for Ammonia straight out of the faucet. I filled the tank with that and dosed with Prime and Stability per the label. I used gravel (rinsed) as a substrate, two decorations (also rinsed), then had one Anubias, one Java Fern, and one Marimo Moss ball. I also had a tiny bit of Salvinia floating in the tank.
For the filter I lowered the flow all the way, drilled 4 holes in the tube and added extra sponges behind the intake to baffle the flow. The flow seemed fine for the betta. I only had one male Betta in there. I never washed or cleaned the filter stuff (other than the initial rinse before setting it up).
I tested the water everyday with the API Master Kit and did a 25% change every day due to the high ammonia readings. After 3 days of that I did a 50% change with bottled spring water to try to get the ammonia down (all water I added was treated with Prime and Stability and rested for 25 hours before going in).
Attached is a pic...I have not tested anything since the fish died. I was planning on breaking it all down and making it a NPT with soil, sand cap, and a few extra plants (I was thinking a Green Ozelot and Cabomba Green). Is this a bad idea?