[spanko]

My opinion here.

For substrate sand is the accepted norm for this. Less than 1.5" is considered a good shallow sand bed and is what most will do. More than 3.5" is considered a deep sand bed and is a little more challenging. I suggest you do some searches here to determine what is right for you. Adding sand is as easy ads taking a pc. of pvc pipe with a funnel at the top and adding the sand through it targeted at the area you want to increase. This should be done in increments of maybe 1/4 of the tank at a time with a few days in between to allow time for the new sand to populate with bacteria.

For live rock \ rubble adding this to and established tank needs to be done with cured live rock. You don't really want any die-off to be causing any ammonia spike in your tank, especially if you already have inhabitants. Some store see cured live rock but I always put any that I buy into a Rubbermaid container with a power head and heater. The test the water over the next week to see if there is any ammonia. If there is let it cycle with water changes before putting it into your tank. You want the ammonia, nitrite to read zero, and the nitrates to be equal to or less than your tank is.

You can always buy Tufa base rock and rinse it and add it to your tank with little concern. It will not have anything on it to cause any ammonia spike and will populate with bacteria quickly.