1) If you move everything over at once, you might see a mini-cycle, but I'd doubt it. You'll probably be okay since you're not introducing anything new during the move. You might want to consider using new sand, though, depending on how old the stuff is that you already have.
2) Depends on what bulbs you plan to use. I like the actinics, but many don't use them with MHs.
3) I'd recommend 35 or 45g brute trash cans to have on hand to hold rock, water and sand.
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