Spiffyguy:
From your original post it sounds like you have it down. I would also lean away from the miracle grow. There is no question that it will work. I used to use it. I'd go with the FLA aqua farm's f/2 liquid Micro Grow (the whole culture process is outlined on the back of each fertilizer bottle). It is made with aquaculture in mind. I use it and get thick soupy green cultures every week. I also do the concentration method that DrBDC describes, pouring off the top layer.
I would also recommend starting with a pure culture from FAF or a fellow reefer. I always have extra. I would give you some free, but I live a few hours south.
-I use 48" N.O. fluorescent (18 hrs on) with "cool white" bulbs. Shoot for bulbs with a high blue/violet peak on the spectrum, as these colors stimulate vegetative growth in plants.
-Room temp. (75-80 F)
-Salinity is 1.017
-10 drops of Micro Grow/ 2 liter jug
-Aerate like a low boil, no air stones
-Start new cultures (with 1/3 old) every 8-9 days
Also, I read that phytoplankton has a peak nutritional harvest time of about 7 days after inoculation of new culture. That is also under optimum culture.
One last thing, try to be conscious of dumping any unused or "dead" phyto down the sink, toilet, shower or outside. Boil it on the stove first. The stuff can live in fresh or salt water. It can run off to streams, lakes and springs and has the potential to cause problems in native flora and fauna communities. That may sound a little over cautious. Five days a week I see, first hand, how the mismanagement of plants has destroyed acres of pristine land and water.
good luck buddy