Yes - you can certainly add more sand to your tank even after it has been established. Just a few things to keep in mind though:
1. Add the new sand SLOWLY, and over an extended period of time ... i.e. DO NOT add it all at once. You can do it two ways ... focus on a certain section of the tank at a time and get it all complete and then move onto the next section. The other way you could do it is to add a really thin layer over the entire surface, and repeat the procedure the next time around. Either way you choose to do it, try to stir up the bed a little after you have added the new layer. This will avoid suffocating the critters and other beneficial stuff that might already be in the sand.
2. Once you start adding the new sand, remember, that if it has any traces of silicates in it, you might see a diatom bloom in your tank. Do, don't be alarmed if your tank gets covered in brown stuff once the new sand has been added ... just a warning
Very true!! Unless you're getting it for free, I'd personally go with regular marine sand. That sand, when mixed with the sand from your established tank, will turn to Live Sand in due course of time!
k ya that's what i would do was add dead sand but ya that makes sense. I need more sand cause i had reallyh bad brown algae and sucked it up and what came with it was a bit of sand so ya. Thanks