Congos don't nip.
I've kept them for sometime. They go after eachother, but never cause any damage.
I really would not use laterite. It has little use in a non CO2 tank.
Yes, CO2 will make a huge difference and is the reason why so many folks are hooked on planted tanks. A decent gas tank set up will run about 125$ depending on how and where you get things. But you can T off this tank and add CO2 to as many tanks as you want and the refills run about 10$ once a year for 150-200Gallons of tank.
If you really want to do the plant thing, 220watts of PC's and the CO2 is a good idea.
Get the Flourite from SeaChem, it should not cost you much from the LFS. Do it 100%. Add about the same deal as the non CO2 only a aboiut 4 handfuls of peat and close to the same amount of Mulm. Plant dense from the start and plant heavy.
Also see about getting these 4 things:
KNO3
K2SO4
KH2PO4
Traces(SeaChem Flourish, Tropica Master Grow etc)
Unless your tap water is super soft(GH and KH 3 degrees or less) you will not need much else.
Unlike SW, FW plant tanks are easy to do water changes and re set with nutrients.
This way you can keep a good range of nutrients in the tank all the time and the above chemicals are cheap(except for the traces).
Don't be scared of the CO2. It's the best investment you can make with plants. Flourite is another.
Good lighting is nice but you can do great even with a cheesy shop light and a good CO2/nutrient dosing routine.
Generally: more light means less room for error and the faster the whole system grows.
Like driving, getting in a wreck at 30 mph is not as bad as 60mph.
Thanks, I think I have just about all the info I need. Three more questions: Is a Magnum 250 Pro adequate for this tank filtration-wise? And what type of CO2 reactor would you recommend for a 75 gallon tank? I'll take a trip over to Home Depot tomorrow and see what I can find. The fixtures seem very cheap, although according to the website, each fixture can only hold one 20 watt (24 in.) or 40 watt (48 in.) bulb, leaving me only room for 80 watts max with a double fixture...What am I missing here? Do the T-8's have a higher output?