History - I have 5 discus (5-6") - 3 are very healthy, the other 2 were a mating pair - a year ago they were producing eggs every10 days or so for about 6 weeks. (Couldn't get any to hatch). Introduced some new plants to water - all of the discus got sick. Ended up treating with metronidozole and eventually got them back on their feet - at that time put in an ultra violet light. The male discus (tourquoise) never really got back 100%. Off and on for the past year he has developed clamped fins, the start of ick (I usually start treating the whole tank with Quick Cure when this happens). He gets a half moon type whiteish circle at the back of his body (see picture) and has shrunk down to half the size he was when I got him. I have a 140 gallon tank, an assortment of louches, neons, catfish,algae eaters, ghost fish, one 12" pleco (all healthy and no bother to the discus). Temp - 86, ph 7 - 7.2 - all tests OK. Do 30% water change once every 10 days, about 10% every other day. What should I do - I am concerned I will do more damage to him putting him into a tank by himself (1 have a 10 gallon emergency tank) and I don't want to put the female with him - she is also smaller than she started and although she has black stress stripes her over all health seems OK. I gave him a salt bath yesterday and it took most of the day for him to recover - I don't know what drugs to treat him with. I am hesitant to treat the whole tank - any help would be much appreciated. Also, ever since we put the ultra violet light in we have been getting a black substance on our rocks and the cord to the fibre optics light. Comments??