Heavy breathing and not eating

[Kringle]

Hey, I have an average size Head and Tail Light Tetra who all of a sudden started to breathe heavily and not eat. The tank has very low ammonia and nitrite levels and also has decent oxygen levels. I did notice he had black/gray areas on him from a couple months back when there was an ammonia spike but he never lost the spots and never stopped breathing heavy after quite some time. There looks like there are a few pieces of this white stuff on him, 1 piece on each side and one on the top fin, it isn't ich. I'm wondering if it is a bacterial infection or something but I don't know what to do. How should I treat it?

 

[Kringle]

I also have an Orange Dwarf Lobster in the tank, if I treat with Melafix will it hurt the lobster?

 

[Rocksor]

What is low ammonia? You should have 0ppm ammonia and 0ppm nitrites if you have sufficient biological filtration. Do enough water changes to keep ammonia and nitrites below 0.25ppm, and use Seachem Prime as a water conditioner. You will have to test for ammonia and nitrate everyday using liquid tests.

 

[Kringle]

The tank has 0 ppm ammonia and nitrite. The other fish are fine and very actively swimming and eating, its just the one fish who looks sick

 

[Rocksor]

Post a picture or video, it's harder to diagnose without one.

 

[Kringle]

There's a video, he just stays in a 1 spot for the most part and is completely stressed out. All the tank parameters are fine.