Planted Tank Guru
Join Date: Dec 2006
Location: New Orleans, LA
There's no reason that wouldn't work, but I bet you could do a whole 55g with 2 9L bags. One 9L bag fills two 10g tanks with a little to spare. A 10g is 20"x10" x2 = 40"x10" quite close to a 55g = 48"x12".
Instead of pots, just put the aquasoil down along the back, or perhaps just in the corners. Use a plexiglass divider if you like to help. Then lay the sand down. You could get away with a bag or less this way.
That tank you linked is spectacular, but 55g isn't 375!