I would take a look here.
http
/www.fishforums.net/index.php?showtopic=153493
Have you lost any fish to these symtoms.
Loss of appetite
Progressive thinness
Sluggish movement
Folded fins
Eye protrusion
Dark coloration and granular appearance of the cornea (this is the first sign in Angelfish).
Skeletal deformity
Hanging at the surface
Skin defects, including blood spots and open wounds that may ulcerate
Black spots, or overall dark coloration (in Cichlids particularly).
Fin rot, characterised by the outer rays falling out.
Scales loosening and falling out
General swelling and scale protrusion (as in Dropsy)
Also check all fish for these signs.
Long stringy white poo or clear mucas poo.
Worms prutruding from the anus.
Enlarged anus or red inflamed anus.
Fish being skinny or bloated.
Sunken in belly.
Fish swimming on there sides.
Bent spine.