Thanks for the help! I'll be sure to flush the rockwool before using it.
I'm still a little confused about this rockwool pH stuff. Basically, I'm just wondering if I need to keep the nutrient solution pH lower than the normal 5.8.
In an ebb & flow system using rockwool does the pH of the entire nutrient solution rise because of the rockwool, or is the pH only higher INSIDE the rockwool cubes?