Hydroponic mold question ( keramzite + rockwool ) Im not sure it is mold.. but looks like.

Sure you can save them. Dip your cubes in a water + h2o2 solution with 12%h2o2 its 0.75-1ml per liter of water, also add it to your nutrient solution at this ratio and regularly clean your buckets with higher amounts. Handle Hydrogens Peroxid witch caution, its recommended to wear gloves and eye protection. It will not only end the mold it will also prevent Algae from growning (this would be a common problem in non black buckets), breaking down nutrients making it more accessible for the roots and supply them with extra oxygen when degrading. Since it degrades quite quickly you need to refill every 2-3 days. An other way to deal with this would be beneficials, if you would have had inoculated them early with microbes/bacteria/fungi the mold wouldn’t have been showing up like this. Spores would be there bud the beneficials would overpower them. In hydro you will either go steril (with a desinfactant agent and best with UV) or go with beneficials to maintain a healthy rootzone. There are pros and cons for each way and they still wont give you 100% security when it comes to infections, there are Pathogenese wich can become resistant to desinfactants (in this low ratio where its still ok for the roots) and beneficials can die if things go wrong. I like to go with beneficials and if run in trouble lower pathogen pressure with an desinfactant and give fresh beneficials afterwards