I bought a blue hippo tang about three weeks ago. It apparently was infected with ich. At that point I did not have a quarantine tank (I know, I know. Don't start with the elitist comments. I'm still learning from my mistakes). The fish had been in the LFS for several weeks already. It had been thriving in my display tank and was eating vigorously. About two weeks after I bought it the salt grain looking white spots started showing up on that fish and several others. I set up a quarantine tank at that time (with an old 20 gallon used for freshwater in the past). I used water and crushed coral from my tank to jump start the cycling process. I elected to wait while the fish was still vigorous for a week. On Sunday I put all my fish (the hippo with a yellow tang, two sebae clowns, a six-line and a strawberry pseudochromis) while they were all reasonably healthy; the white spots seemed to go away then recurred but only about two dozen spots on the hippo which had the infection the worst). The next day the fish were still vigorous and ate well. By Monday evening the pseudochromis seemed to start lying around. By Tuesday it had died and more fish became lethargic. This am my six-line died and the other fish are gasping and lying on their sides. What did I do wrong?? I had been gradually bringing the salinity down (usually removing five gallons at a time and then adding 1 gallon back hourly of premixed aerated preheated saltwater with a specific gravity of 1.010. The specific gravity Monday was down to around 1.017. I am measuring specific gravity with a floating hydrometer and have a refractometer on order and didn't want to shock the fish as long as they were reasonably healthy going into the tank. By Tuesday I have started 25% water changes twice daily as my nitrites became detectable. Now my parameters are as follows: Temp 80 pH 8.2 Alkalinity normal Ammonia - 0 Nitrites - 0.2 Nitrates - 20 Specific Gravity - 1.014 I am doing water changes frequently to try to save the fish that are left but my premixed water is gone so I will not be able to add aged water. What did I do wrong? My wife is mad at me that I even tried to treat the ich as she didn't even think the fish were sick. What did I do wrong? Did hyposalinity kill my fish???