How big is your DT? The live rock you have along with good husbandry might be able to keep your nitrates at bay. I'm not knocking deep sand beds, being that I've had one for a long period of time in my DT without any problems, it's just that I've come to realize that things don't have to be so complicated sometimes. Don't overstock, don't overfeed, try to remove as much detritus as you can on a regular basis and you should be ok IMO. Other things like a refugium, GAC & GFO might not be needed as well. JMO, GL.