Water Quality in My Ecosystem

I've learned a lot since the begging of this project as a result of having to take care of fish in an aquarium. I've learned that a high ammonia reading is bad because it can kill the fish. Also, high nitrate can kill fish. However, the most sure way I've learned to kill fish is not dechlorinating the water. The problems I've had in my aquarium was high ammonia so I added bacteria to break it down. The success was that only one of my fish died, and even the one that died didn't die because of me, he was just sick by himself.