Water parameters (tested with API Test Kit):
pH - 7.9
Ammonia - 0ppm
Nitrite - 0ppm
Nitrate - 40-80ppm
--
KH - 240
GH - 180
(i.e. very hard water)
Edit:
This is a 40 gallon tank, established over 1 year ago. In addition to the below sick fish I have 2 mollies, 5 barbs, 1 zebra danio, 1...