Pangasius Shredding Skin? Please Help Asap!

[proppaskint]

hi all
sorry to make this a quick question, but i urgantly need help for my pangasius. about 10 days ago, i noticed some small white furry marks in different parts on him, so i added a bit of melafix,after a 20% water change. problem seemed to get worse over the next couple of days so i did another water change and added a tiny bit of aquarian salt. problem still looked like it was getting worse, so over 2 days i did 2 more water changes and made phone calls to my local fish shop (who sugested it could be velvet) and did days of research on the internet. ph levels and nitrite nitrate levels were fine 4 days ago. never had a problem with him b4. all my other fish are bright and perfect.
how he looks now... he looks like he is shredding his skin or 'peeling' in places, but the skin is white.(the only way i can describe it is like a human with really dry skin, or peeling after a mild sunburn!). there are some white bits on both his eyes. today he looks like hes got tiny dimples underneath his skin. his tail and fins started to look tatty. hes off all foods,although did nibble 2 strands of bloodworm today. hes also started gulping air quite a lot. started treating with sabbactisun and parazoryne 12 hours apart. dont know what else to do. hes 1 of my oldest fish and really dont want him to die. please please please can somebody tell me whats wrong so i can treat him asap!! any help is greatly appreciated.

 

[KittyKat]

It sounds like you started with fungus, have you tried using a real anti-fungal medication?

I am not sure, but do pangasius tolerate any salt at all?

This species is it? The most common one (aka iridescent shark) is schooling fish, do you have only one or 6+?

Again, what size fish tank is it in? The iridescent sharks grow to 3ft and require something the size of a room for a fishtank.