Help! Sick molly!

[Salski]

My bf's Molly is covered in white fuzz or slime an she has some red marks on one side.

She is hanging out in the bottom corner of the tank out of the current, and seems to need to swim furiously to stay in one place. She was being carried by the current before and couldn't swim against it.

Yesterday she seemed to be having some trouble staying afloat (spent some time nose down at the bottom of the tank). But then she corrected herself. Wish I had paid more attention then!



What can I do to save her? She is definitely my favourite Molly!

 

[Salski]

Additional info:

Ph 7.8
Ammonia: 0
Nitrite 0
Nitrate 10-20ppm

She perks up at the sight of food, but not sure if she actually ate.



For a colour comparison, the above photo was taken last week when she was nice and healthy. She has lost almost all of her colour on top.

Any help is really appreciated!

 

[Salski]

My Molly sadly passed away overnight. Is there anything I can do to stop the rest of the tank getting sick like she was?