Growing in a large cabinet with a floood and drain set up with 600 watt Air cold light. Why do I have green mold on top of my rockwool cubes ? 6" cubes
It's algae. It'll grow when the medium is well-lit and continually damp with nutrient solution. Cover up the cubes with some black-and-white if you want it to go away.
Most people don't notice any significant problems from it.
I encountered the same problem using a rapid rooter plug. Yes cover it someway some how so light doesnt penetrate it... Also very gently get some sharp scissors and cut the mold out ..