A few questions about a new setup

[jennsimm]

I have started setting up and getting my aquarium ready. The problem is that the tank is a cube, 24 inches square. I have a question about placement of the powerheads. I know I at least need 2, but would 3 be better? Just for placement of them, im not sure if I need 3? Also, I am ready to buy my filter and skimmer today or tomorrow. I have been reading different things, and would hang on ones work for me? Another question..I have the book 'the new marine aquarium'. In it, he says to put the lr in and not put the sand in after the tank has cycled. I was under the impression that you put it in before the cycle, after you add the lr? Which is correct?
TIA...
Jenn

 

[darknes]

Add the sand before the cycle; I've never heard of waiting until after the cycle to do that.
As for the powerheads, what size tank is it?

 

[sankysyuck]

Yea you want the sand in there so bacteria can colonize in there.

 

[mudplayerx]

For a reef tank you want 20-25 times gallons per hour flowing through your tank compared to the size of your tank. For example, if you have a 20 gallon tank, you want a minimum of 400 gallons per hour flowing through the tank.
Good powerhead brand names have the gallons per hour listed on the box.
For a fish only tank, you want about 10 times the gallons per hour.
As far as the live rock and sand, put those in during the cycle.