Hey mate,

I'm also using a 600w hps i have 3 under there at the moment but there getting way to bushy one was FIMmed and the other left to grow. So personally i'd stick with 2 really well fed plants or 4 and go SOG style as i've heard thats reaped very good results. At the moment my plants are super skunky and they have filled the whole gym room (10metres long by 8 metres wide with 16 foot ceilings) with a very strong sweet aroma :thumbsup: this has only come about recently but i think the fact i have my lights so close is keeping them warm and kicking up the smell.

As for the lights there's all sorts of theories around the site one i've heard that worked for me is "put your hand under the light until you can't keep it there for a minute then raise it 2 inches (can't remember who posted that but kudos to them)" i have slowly put them a bit closer as the plants have grown bigger, mine are about midway through flowering and i have the 600w around a foot from the top cola's and have now added another 400w (as of today) to the side just for a boost and that is also roughly a foot and a half from the bottom buds with a bigass satellite style reflector. Everything posted is just info from my personal experience. :weedpoke:

Peace :hippy:Bio

Edit: shit just read your actually asking about hydroponic, mine are just indoor and in soil, anyway might still help :stoned: