I am very experienced – decades of keeping reef tanks, planted tanks, all sorts. Currently have three 200G+ tanks – full reef, planted discus, african cichlid. All doing well. A couple years ago I established a 3 gallon fish bowl with no filtration, heater, or even an air stone. I set it up in my kitchen and did weekly water changes from my planted discus tank with zero nitrates. There is no bio filtration in the bowl, yet the five white cloud minnows (that live at room temp) have all thrived over the years and have bred – there is now a sixth. With this success, I set up another bowl, but at my office in another town – too far for water changes from the established tanks. Instead, I use tap water (100ppm) treated with Prime. Everything else is the same, including yet even more frequent water changes. Yet these fish keep dying. It must be either 1) over dosing Prime or 2) the used fish tank water from the established tanks has bio/bacteria in the water column. Since the water is generally fresh tap treated with Prime, there can't be any ammonia in it. I have read that overdosing Prime starves the water column of oxygen, which seem like it may be a cause there. My next step is to stop using Prime and instead use tap water that has been left out for a couple of days such that chlorine is eliminated and temp equalized. Does this make sense?