Mold on my rockwool?

Hello,

I'm a first time grower. Started with SH bubbleponics, switched to DWC buckets when the plants got big. I have some white "stuff" (maybe mold?) on most of the rockwool cubes. Pic attached. The humidity in the grow space is usually 50 to 60%, hardly ever above 60%.

The white stuff has not spread to the plants, but I'm concerned it might. Any advice is very much appreciated!

I think I would clean all of it off and then cover the rockwool with a piece of black plastic or something light can not get through.. I know that works to keep algae from forming on top of the rockwool... I have never seen that before what you are experiencing... What is the humidity at in your room, mold only grows in a humid environment. Good luck

dont use black plastic all around it. It can sufficate your plant but you can cut a wide enough piece to drop down and cover most of the light . just dont wrap it all around the rockwool.. also put it in soil or whatever you plan to do if its ready.good luck

Thanks guys.

biggun - Humidity is never above 60% in the room. But that rockwool stayed very very moist for weeks because I was using a bubbleponics system and kept water flowing to it constantly. That is no longer the case.

marijuano - These plants are 6 weeks old, hydro, so the plan is to keep them in that rockwool to stay.

A friend just suggested to cover them hydroton rocks to keep the light off... same theory as black plastic

good choice with the rocks when i usedthem i did the same thing . just put the rockwool lower so u can completly cover with rocks works gret

It is probably just some hardwater minerals. Calcium, I mean. When the rockwool dries this is left behind, or some other residue. I get algae in a week or two with rockwool but it not a prob. Just cut some squares out of paper, several or black contruction paper or the most perfect option is to buy the covers at a hydro store. They have cover made of plastic or panda film to cover all things hydro. But that is for algae which is green. So I hope for yu dude that is just hardwater but if not then what nutes, maybe take a solution of nutes, not plain water, and pour it over the top. Grodan says never use plain water as the plant get out of whack. This should flush any other salts. Periodically do that to rockwool that gets solution on it.

I agree with tea tree. It looks like some salt buildup now that the rockwool is dry. Is it fuzzy looking, or more chalky? Is it growing at all?

I think you guys are right - probably hard water residue. Its more chalky than fuzzy. But for safety's sake I scraped it off and covered the rockwool with hydroton rocks. Thanks for the help!!