i take it that you have a rockwool starter plug sitting in a cup of water? just a little word of warning, if you let the rockwool stay sodden and let the roots grow into standing water for to long then you risk root rot. also the lack of oxygen to the roots will slow growth. a simple thing to do is to tip the water away and let stand "dry" for a coupple of hours a day before adding enough water/nutes to keep it damp/wet untill you can check and ajust the water again. when i use nft i only run the pump for 15mins every 2 or 3 hours when seedlings and only 15mins every hour when fully grown. rockwool will hold a lot of water. a hell of a lot more than soil.
sup thug. no its not a starter cube nor is it in a standing cup of water. that blue thing its in is my equivalent of a net basket the 4' rockwool cube is stuck in there and the bottom is knocked out. i just moved it from the res for the pic. root rot has not been a problem yet. light is the only problem. but ill be gettin all crunked up with 4oo watt soon. is the hps system hard to set up?
If I'm not mistaken, the 400w system should be pre-assembled, maybe with the exception of plugging a couple things in here and there and just maybe even the necessity of installing a *Gasp* glass screen! Heh, yeah, sorry for being a smartass. =P ~Lycanthropy