Hi jkrustie.

I had that problem recently i just filled the bottom of the tray with hydroton clay medium and had about 2 mils of nutrient solution at (cf 10) on the bottom for the roots to grow into the main reason i did this was was to protect the roots from the light.

Hope this helps .
floyd2zapper Reviewed by floyd2zapper on . Rockwool grow questions Heya This is my first serious attempt with growing soiless in rockwool. I've got some nice Diablo(Next Generation Seeds) seedlings in my 4"x4" rockwool blocks. Growth looks good, and after 5 days going from the 1" cubes to the 4", the roots are starting to come through the bottom. This is where I have a question, how long can you allow the roots to grow through the rockwool cube? I have them in a cloning tray, so the roots will presumptually grow in the tray, sucking up run off Rating: 5