Adding more sand to established reef tank

I have had my tank for almost a year now and everything seems to be going fine (except for the loss of my Naso a couple weeks ago). I got the system from someone who had it for 5 years or more, so it is well established. I want to add more sand for a deeper bed, it only has about 2 inches, and that is not all the way around. Would this cause a cycle in the tank? I would like to probably add 20 lbs or more to get a good 4 in deep bed. What do you think? Tank info below

45 gal with 96w PC (upgrading lights for Christmas, even though this does surprisingly pretty well)
60-70lb Live Rock
paired Perculas
Electric Blue Damsel
Foxface
Green Spotted Puffer
Haitian Condy Nem
Green BTA
Long Tentacle Nem
Various Soft Corals/ Zoas
Very Few Stony Corals

 

What I have done in the past and will continue to do in the future is buy some dry sand, I wash it in some RO water then add it a cupful at a time. If you use dry sand, you shouldn't have any problems adding it all at once, but if you want to be safe, you may want to do this over a few weeks. I've never had any trouble adding dry sand to my tank. I actually do it quite regularly.

 

So if/when I buy the new sand, don't buy "live sand"? Do you just lay the new sand on top, or kind of "mix" it in?

 

I added sand after mine was already set up and I just got the dry stuff. Didnt seem to suffer any ill effects. You should be able to mix it around a little.