We used STG (or SureGrow), the loose-fill like it looks like you have, and we begrudgingly went back to rocks because the STG holds too much water (we still use the STG 'cubes, surrounded by rocks in the net pots). In DWC the STG loose-fill was an issue for us, and I hate stepping on those damn rocks!

I'd agree with some of the previous posts - your water level is too low, the water level needs to be about 1/4-1/2 inch above the lowest roots (at a minimum), at least that's my 2 cents.
bhicks Reviewed by bhicks on . root length ? please help My bubba kush is about 6.5 weeks along now and I suffered some heat stress now all is better but the roots are not growing in length I am using recipe for success nutes and started with 1/4 nutes There are a lot of roots but they are not growing longer than the bottom of the pot Rating: 5