Microworms producing oily substance

[Kalinkacat]

Hi Everyone,

I've come across something new with my microworm cultures and wondered if anyone has had this and can tell me what is going on.  The culture is teeming and when I put the worms into the tank it puts an oily substance that floats on top of the surface.  The culture itself also looks kind of dry but is teeming with life.  Any ideas?  Thanks.