New Beginnings

Hello all-

I've recently decided to begin an experiment concerning the breeding 
behaviors and distinctions between native Papiliochromis Ramirezi and 
asian bred varieties, of course pending the honesty of my sources for the 
fish.  As I outline my procedures, I have been out collecting rocks and 
substrate materials to use in the tank enviornment.  I will house two 
pairs of native in one 20g tank and 2 pairs nonnative in another 
identically set up tank.  I have cut and bored the rocks to the extent of 
where I will have identical rock structures and homes for the two tanks.  
For filtration and heating, it's a simple canister filter and heater, 
nothing special. 
As far as the sunstrate material goes, this is where I need a little bit 
of help or some suggestions.  Since I have gone through the trouble of 
acquiring rocks and river sand from surrounding areas (cleaning properly 
of course) I figure I mine as well go full bore and plant my tanks with 
live plants.  For the substrate I have some Washington river sand from 
the Big Chief River, as well as some coarse to finer granite gravel which 
I created by finding finely weathered granite and crushing it in the lab.  
So I plan on mixing the two together (the river sand is medium size to 
fine sand) and then covering it with the crushed granite for athestic 
value (have to have something to look at that's appealing!) Now I've 
heard about such things as Laterite and others, for which I have never 
heard of before.  That as well as CO2 injectors, some people say you need 
this stuff and some say you don't.  The CO2 injector is out of the 
question do to financial constraints, however people say I cannot go 
without the Laterite.  Please give some suggestions if you will and maybe 
a source of where to find such a thing as Laterite, for I have not a 
knowledgable aquarium staff nearby.  
Thank you very much!