im about to begin my first planted tank in a 55g. i have the red sea
co2 setup, 4 40watt flourescent bulbs, but the red sea substrate was too
expensive so i settled on this box of laterite from petsmart. i have no
idea what it is but i followed hte directions and mixed it into the
gravel. so my questoin is, is this laterite stuff any good? it seems i
have to periodically add new laterite, how do i do this with an
established tank without messing up the roots, etc? also, what plants
do i start off with? anyone have online sites to order in bulk from for
cheap? thanks.

Laterite works fine - it's just messy if you like to gravel-vac. I've
never added more laterite to a tank - maybe you would have to after
many years. Start off with some fast-growing plants like Hygrophila,
Rotala indica (or rotundifolia), Bacopa, valisneria, or saggitaria.
Swordplants, anubias, and crinum are easy too. Add Cryptocorynes
later, once there's some nutrition in the gravel. Avoid the really
high light plants.

I have ordered from http://www.aquariumplants.com/. They have some
good assortments so you can try a lot of plants.
http://www.thatpetplace.com has nice plants too, and plant packs for 55
gallon tanks.