Green on Rockwool

[godsbackyard]

There is some green color substance starting to grow(?) on top of the rockwool by the stem on some of my plants. What is that? is it bad? If so, what can I do to fix it?

[bonbon]

Algae growing on RW is quite common and harmless to the plants,nothing to worry about....bonbon

[mahatma]

In fact, the green alge is a good sign that your nutes and ph are A.O.K. Once when I grew with rockwool the plants did great a long as there was alge growing. But later when the alge died, so did my plants shortly thereafter. It's a sure sign that if the alge dies you have a problem and need to correct it quick.