Mold on rockwool?

I'm getting what looks like green mold on my rockwool cubes in a stealth hydro system.
Is there anything I can put on it to stop it or is there something I need to do?Is the rock wool supposed to dry out once the plants get going?

I put a lil hydroton in the nets then put the cube in on top the feed line and then filled in the nets with the rest of the hydroton.

The green stuff algea, not mold it won't hurt anything. It forms when the rockwool is wet and its exposed to light. It is annoying at first, but the best option I've seen for this is to cover the exposed area of the rockwool with black plastic.

If it bothers you, take a serrated knife, and cut off the top 1/8 inch of the cube, the green is really shallow. Then you can cover it.

I was just worried it was some sorta mold that was gonna affect the plants.Thanks for the info guys.