???????
240 gallon 5/8" thick glass plus water...2900+ lbs....crushed coral and gravil substrait...96 lbs.
The substrait in question is about 1.5 to 2 inches deep...not a whole lot of usable real estate...unless your a guppy.
I had a 135 gallon tank set up and running this way for slightly over 17 years...no excessive gravil vaccuming...no huge build ups...
This has to be the silliest argument yet...
The gravil substrait provides additional living serface for extra BB that converts ammonia/nitrite/nitrate an so is FAR more valuable than the TINY extra amount of water you have with a Bare bottom tank.