Help I think my moor has velvet

:help: I have two moors one big and one small(er). The smaller one has a white film above his gills, he's moving extremely slow, he won't eat, he's at the top when he is usually at the bottom, he did not try to swim away when caught him to put him in a separate bowl, and he has a very long, thin, white string of waste hanging from him. I really don't know what he has. I thought velvet because of what I read on-line. The difference is they talk about a rust, goldish color, but this is a white film. Because he is black, the white is very apparent. I don't know how to treat the water with salt or even if I should. Any info would be appreciated. Thank you!