gill problems

[harling]

my comet has dark filament matter extruding form his gills and is very unwell. What could this be?

[Fern57]

This sounds very much like 'bacterial gill disease'.
The diagnosis and treatment is too long to put in here, but if you follow this link:
http://www.fishdoc.co.uk/disease/diseasehome.htm
There is a whole page on the subject.
Good luck, and I hope you can save your comet.