Fresh water sand bed

[shawmutt]

I'm making plans for my Lake Malawi tank, I have two weeks to get it done. I'm going to start from scratch, with fresh r/o water and everything, so I can scrub my tank and get rid of the nastyness. I'm going to start from the bottom up, first a bed of sand, here's my first two questions:

1. With a bed of sand, how deep should it be in a freshwater tank?
2. I'm assuming argonite sand is the best bet...is this correct?

Then I'm going to put the rocks in and keep them in place with silicone. I'm modeling it after some great pics I saw on the net at http://www.tropheus.info/riftlakes/c...foto_uv_e.html . I've never aquascaped with rocks before, so I have a few questions about those as well:

3. Should the rocks be piled in back of the tank, or in the middle?
4. This setup does not include plants. I've never had a tank without plants--are there many differences or some things I need to watch for in a tank without plants?

Then I'm going to add the water. I'm adding r/o water and r/o right to make the water hard and with a high pH. Some more questions:

5. With the argonite sand, is the pH going stay at a certain level?

Now about lighting. All I have is the light that came with the tank, a 20 watt fresh water bulb. It's enough for my dim South American tank, but not enough for this one. I was thinking about getting an all glass top and maybe getting a pendant mh bulb.

6. What [acronym:5bd8a31f93="Watts Per Gallon"]wpg[/acronym:5bd8a31f93] should I aim for?
7. What is my best (read "cheapest" ) option for lighting?
8. Are mh lights dimmable?

And finally:

9. Am I on the right track or am I way off base?