okay, so in my small 10 gallon that I set up for quarentine, I filled it about 3 quarters full with water from my tank that has been set up for over a year with no problems, (then topped it up with new water) and 3 plants from the established tank. I did an ammonia test that read 0, but regardless, one of my fish in quarentine still died. So i went out and got a new test kit, and sure enough, the ammonia tested at about 0.35. I did a 50% water change and that lowered it, but what else should i do?