Quit double posting man. Put that fucker in some dirt (Sunshine or FFOF) and give it some 1/4 strength Miracle-Gro. Top it like Uncle Ben and wait. Then give it 6.5 TAP water with conditioner and 1/4 MG every watering. Cal-Mag never hurts either.
raise the light a few inches ,is it a fluro? Also i agree put the cube in some medium, perlite,hydroton etc, the roots have no where to go and the plant will stress.