Hospital Tank Question About Black Spots Under Skin

[bluesfan]

Hi, i purchased 4 gouramis i noticed 2 of them had black spots under skin so i put them in separate tank to try and clear spots from fish they have now been in tank  3 months  spots still there but got no larger or seem to affect  them in any way would it be safe to put them in with other fish as the 2 other gouramis have not been infected at all  just wondered if time elapsed is enough cheers.  

 

[Ninjouzata]

I'm not sure what that could be as I'm quite inexperienced with fish illnesses, but it might help if you could post a picture

 

[Chad]

Can you post a photograph?