No one, Sprung, Delbeek, Jaubert, etc has conducted a true study on Remote Deep Sand Bed (RDSB) size to total system water volume ratio. Even Leng Sy's Miracle mud system reccomends a fairly larger fooprint per total system gallons.

http://www.ecosystemaquarium.com/pro...tructions.html

When the guy on Reef Central came up with the 5 gallon bucket system, this was the first time someone with high nitrates was able to lower them with a smaller deep sandbed.

Before this idea came about, most people effectively using a RDSB were using standard sized tanks usually 55g or larger for their RDSB. Or they were using a large portion of their sump, built especially for a RDSB, usually the footprint of a 10 gallon tank or larger.

I would speculate that most people today use a remote shallow sand bed with vegatation culturing to lower nitrates and phosphates.