I am now in the process of building the first pool for the Rays under the shelf. I ended up going with wood and pond liner, and no steel frame for a couple of reasons. First, due to the position of the pool, I only needed to make 2 sides of the tank. I also needed to make a raised platform out of 2 x 10's, or there would be no way to use a sump. So now I have room to plumb in a drain and run it into my furnace room where the common sump will be.
Pool number 2 will be very much the same, except I'll use a backwall of foamboard since it is on an exterior wall.
Pool #3 is going to be the real fun one. Pool #3 will be above pool #2. I am sure that a platform made of 2 x 10's on 10" center will be enough to hold it. but I need to measure some things to make sure I have clearance for 2 x 10's and still be able to access the pools. It still has to fit under the ceiling.
Pictures to come soon.
Mike