ebb and flow questions... media and timers

Hi, first time using hydro and still getting things set up... heres the questions, and thanks for any help you guys can give!

using 400w mh/hps digital balast, in a homemade cabinet 30" x 24". already germinating using florescents and 1.5" cubed rockwool. I want to use expanded clay pellets in mesh bags.

I'm guessing here, but I have my timer set at 15 minutes on, 45 off, around the clock. Is this about right?

Also, I want to run 5 plants by 4, totalling twenty (i went to college for math, can you tell?) do I have enough room for my sog?

and finally, I'm using advanced nutrients sensi grow and bloom. should I be using another product for rooting and germinating nutrients? only using water at this time with the lights on for almost 20 hours a day.

thanks again for any answers to the questions! rep for any who have some sage words of wisdom!

I am using the 1.5" rockwool, and after they look good, i transplant them into 3/4gal each of hydroton. Just place the blocks in the media. The Wool stays wet for a long damn time, but its so little, dont fret about mold. The hydroton will hold moisture longer than you think. I had mine on a 4x's a day schedule, and it seems to be too much, even under a 1000w at 8". With my younguns under the 400w at 8", I set to flood for 15minutes, twice a day. At flower and the 1000w, im gna flood 3x's a day.

I ran a test on my hydroton. I let one plant sit outside the water source. Even at full flower, it didnt seem to show water stress for about 3-4 days.

Im using cloning powder for clones, but just got some clonex gel. Same chemical, just wanted to try the gel. You shouldnt need ANY nutes to germinate, just ph'd water. the plants start life with a couple weeks of their own food. Perhaps you can use a tiny bit (1 drop per gal) of vitamin B (superthrive), after they show some roots, but NO serious nutes until 3rd leafset. I used Advanced 3part for an entire grow and had good results. With the 2 part, you should do really well also. Since then, Ive dropped a fortune on Adv nutes. Prolly didnt need more than the 3part and overdrive, but oh well. Anyhow, good choice on nutes, dont be afraid to call AN if you have ?? about the use either.

Not sure a SOG is the best method for yield for a new grower. Seems like the plant will take the room you give it, and want even more. If you can run the 400w in the cabinet w/o heat issues, Id say you could cram 20 in there. Not sure youd get more yield than you would with 12gals tho. Remember to check your local laws concerning ammount of plants.

Best of luck to ya!!