Cured a new tank syndrome using an existing fish tank and swapping water from one to the other until all the water had been cycled through 100%. Only do about 1/4 of the water at a time then back to the one it came from. First drain the new tank about 1/4th, then drain water from a cycled tank poor it into your new tank. Then take water from your new tank poor it into your older tank. Continue these steps about 6-8 times to achieve your best chances of curing new tank syndrome. This will put free floating benificial bacteria into the new setup and allow you to save new fish before they die. I saved my 2 new 4 inch arowanas. Now they look better then when I received them. Hope this helps someone else save their fish someday.