black blotches on clown loaches

[cheon]

hey guys
i been noticing black blotches on my clown loaches i am pretty sure its a parasite. should i move them to my q tank?are my aro at risk?how do treat this?could this be from my gravel not getting cleaned?
i do a 30% water change every week with prime and salt added.tank is a 160gl tank mates are shovel nose cat,bbxb,sr,gloden nugget,1chiclid.
thx
chris

 

[cheon]

and i test my water every 2 days and its alwayz 0ppm 3 ways.

 

[DaiDee]

got any pictures? I've had clown loaches in a tank with black 3m sand before and they started getting stained black. They are in a barebottom tank now and they look fine. I think it's just the gravel...ever try to clean 3m colorquartz? lol if you run your hand through it, it'll turn black too.

 

[cheon]

Bump

 

[CORVETTE]

I ve read some where this is a natural occuring thing. All of mine have had this after a certain size. I'm not really sure but i believe it was passed through bird feces and really doesn't harm the fish.