home depot will most likely carry only silicate based sands (used for making cement and palyground sand). if you buy silicate based, this is gunna cause algae problems as well.
check your lfs for caribsea brand. its a aragonite sand and this is what you want to use. should run you less than $20 for a 40lb bag. remember, you want at least a 3" sand bed so you may need 2 40lb bags (that is for the 55gallon, if this is for the 29 gallon, then one 40lb bag will do the job).
you could transfer the water to your tank, but since your using tap water, i would start from scratch and use RO water. once the new tank is cycled, then you can move your livestock from your 29 gallon into the 55.
and i seen your other thread about the yerllow tang. if youre goal is to keep the yellow tang, i would consider bigger than 55 gallons, they need at least a 75 gallon imo and even that won't house them for life. if your just upgrading because you want a bit bigger tank, then 55 gallons is a good place to start.