Ideal depth for reef tank?

[surgeonfish]

My current reef tank is 48" deep and almost 6' to the back corner. I find it too deep for a reef tank as the bottom is only accessible by using long tongs (very frustrating). I was considering converting it to a fish only system and starting a new reef tank in the basement once we start renovations (not again). I was thinking of a 100-200 gal system. How deep should I make the rectangular tank? Should I go for 24" or 30" deep? Does anyone with a 30" tank find it too deep? For once I want to be able to reach the bottom of the tank with my hands.