We purchased a 36 gallon aquarium last night. We followed all set up instructions given at the pet store. We used API Quick Start for the water. We put in a few mollies, some guppies, and an angel fish. All were dead within 3 hours. I took a water sample to the store today to be tested and everything was in the good range. It did register that the water was hard. Thinking back on all the goldfish I had as a kid I thought maybe we couldn't go wrong with them. So, we bought a black moor and two orandas. Within two hours the black moor was dead and the bronze oranda. The other larger oranda is still alive. The water tested ok, the water temp is around 76. I have no clue what to do next. Any help is appreciated.