Just starting. Bought a small clear plastic container from Walmart (Sterilite brand) and am checking now to see about the toxicity of it. The water in the tank is well water, and I have no filter system yet. Into this tank I put one plain guppy, one fantail goldfish and one shubaunkin. The guppie didn't last more than a few days. The fantail hung around for about ten days and also croaked. BUT, BUT for reasons unknown to me the shubunkin is doing fine, eats well, swims around a lot and comes to the surface for breathing . Apparently, he has adjusted to the well water and plastic tank. Should I be worried or just let things go as is. Different "so called experts" have a lot to say about plastic tanks and well water but some side with me and see no harm in my present arrangement. I want to replace the two fish I lost, but am unclear what to purchase now due this last go roung. Any thoughts would be appreciated.