I just recently purchased a 75 G tank that I've set up as a freshwater
aquarium. I'm wanting to feature live plants in the tank (along with the
fish).

The tank came with a single flourescent bulb light hood. I ordered and just
received another light hood--this one having two bulbs. This gives me 3
flourescent bulbs over the tank--each of them 40W bulbs.

I've also hooked up a DIY Co2 system that seems to be running very well.

I've read as much as I can find on getting this setup.

There are a few things I'm unclear on and would like help.

*I'm currently putting 120W of light into this tank. That's still not
considered very high, is it? Is there any way to solve this? I can't fit
another light hood on the tank. I'm not sure what type of bulb is in the
light hoods currently. It is whatever is shipped with an "All-Glass
Aquarium, Inc." light hood.

*My biggest concern right now is substrate. I have a canister filter
(Magnum 350). The base of my tank is exclusively river gravel. Is this
going to be a problem? If so, what should I do? (I can't very easily
change out the substrate in its entirety at this point.)

Thanks for any helpful hints.

Tony