All conditioners break chlorine and chloramine down into nh4 which is ammonia thats locked up for about 24hours giving the bacteria time to react. After this time frame the ammonia is released into the water and can harm the fish. Conditioners do nothing for heavy elements or iron or calcium which is in every water supply. Basically if your entire tank is treated water then you have induced an ammonia spike of 1-3ppm per gallon of treated water. When you include the live stock, decaying matter and things leaching from the rocks or sand bed after its been disturbed you are creating an environment that is easily able to shock most critters. I think youve just created the perfect situation and then the more water changes you do the more you are building up. Im sorry it happened but with as expensive as the hobby can be with mistakes distilled water is about 80 cents to a dollar a gallon. Its better to just look funny atthe store buying cases than to waste hundreds on livestock. A cheap rodi system will work but them small under the sink versions listed here still use membranes requiring 60psi. Most places wont have that. You are wasting 6 or 7 gallons of water per gallon of water created. The will get closer to 4:1 with 60-80psi. Its better to add 50$ with it and get a cheap system that includes a booster pump off Amazon. Im sorry for the lengthy reply