Ahhh???
I have 90 gallon with 6 inch DSB.
That's 48 by 18 by 6 or 22 gallons of water displaced by sandbed.
For a 90, for an established reef tank with a decent bioload I would not see how 50 to 65 pounds of livesand in a 5 gallon bucket would do much good. IT's not to say that it would not have any impact.
A concern I might wonder about, wouldn't there be a point of going from low to zero O2 content like deep down towards the bottom of the 5 gallon bucket? And isn't there a limit on the impact of surface area in relation to the rest of your setup? Size and gallons? On the onset it seems like a good idea. But with limited ability to interact with the water column can it really do alot of good other than leaving it possible for a making a deadspot that could produce harmful hydrogen sulphide?
http://reefkeeping.com/issues/2005-12/rhf/index.php
Not so sure about that idea.
Now if you kept it around 6 to 8 inches deep and put some tubs or buckets you could remove that sit underneath your frag racks on the entire bottom then you might get the best benefit and have a prevention of leading to a major deadspot or possible hydrogen sulphide bomb.