BobinCA,
Osmocote is used as a very thin layer, a dusting, under all of the substrate. I should then slowly release the fertilizers so the substrate has a continuing supply of them, until it finally runs out. Laterite is a form of clay, which has high CEC, and has lots of iron in it, which may or may not be very available to the plant roots. Mulm is a good source of good bacteria, which will more quickly establish the bacteria colonies in the substrate, and those colonies, as I understand it, convert the iron in clays to a more usable form for the plants.
A single T5HO bulb, with the typical single bulb, highly polished aluminum reflector, provides about 40 micromols of PAR at 24 inches from the bulb. Since your tank is 24 inches front to back, three bulbs spaced evenly across the top should give you about 60-70 micromols at the substrate, dropping a bit at the front and back glass. This would be about medium light intensity. Or, with 2 bulb fixtures, two of them - 4 bulbs total - with the two fixtures about 8 inches apart should give you at least 100 micromols of PAR at the substrate level, which would be high light intensity.
The best source of fast growing plants, stem plants, is a local aquarium club, Sacrament Aquatic Plant Society, for example. I think you joined? If not, visit
http://groups.yahoo.com/group/sacaquaticplant/ and join us, then send out a group email asking for plants. That usually gets you free cuttings, but only from the stem plants currently being grown in the group. The next best source is the Swap n Shop forum here.
Vaughn Hopkins