I introduced some gold dust mollies into my aquarium without isolating the first and they introduced some weird disease into my tank. I don't know what it is or how to treat it. One by one, the mollies got thin and weak and died. Then my platty got a fungal of infection, became weak, and died. Then a Cory died with no symptoms at all. Then I noticed ALL of my tetras were covered in white spots. I raised the temperature, added an air stone, cleaned the tank out more, removed the carbon from the filter and added ich medication. I'm on my second round of treatment. No improvement. The one remaining tetra is still covered in white dots, looks like it has its slime sloughing off, and threads hanging from its otherwise intact fins. The betta and last Cory are just fine though. Both are very active and happy. Eating well, etc. the two remaining Molly's are very thin and weak, and that tetra is very active, but looks like hell and is thin.