dieing fish

I have a tank that's been up and running, we tested water it was perfect so we bought 3 dalmatian mollies, two snails, and two African dwarf frogs. One by one the all died. I took water in to be test at a reputable store and they said water was fine, do a 20% water change. Did brought back in it...

Hi I have a 55 gallon aquarium that has been set up and running for almost 4 weeks now. I have now 2 neon tetras, 3 baby jelly bean parrot fish about an inch in size each, and 4 fancy guppies 2 male and 2 females , and 1  4" pleco. I had three more fancy guppies and a black moore  but they all...