here goes..

without tubs:

With.. tubs do not have water or perlite (to prevent sloshing) in them yet. They are air/water tight. Think I should just use 2-liter bottles? Seems like too much dead air..

Tub.. I am getting a third brick to break into pieces to put alongside the one in there, to add more support as the plastic grid is a tad flexy. The water will not touch the grid. Your thoughts?