Ultimate shark and ray tank

So I was out at my parents house this morning helping them fill there hot tub when it hit me. There hot tub has adjustable flow with nozzles that can spin to change flow constantly. It can be set to have a huge amount of flow or less in many increments. You can set any of the outputs to pump air for better surface movement. It has a large mechanical filter that keeps the water crystal clear. It has a digitaly set heater that can keep the water over 100 degrees outside when its below zero out. It has built in underwater lighting. Of course all these options are push button controlled from the outside. And to top it off its well over 1000 gallons.

Now to the point. Iv been looking into setting up a large shark and ray tank. What could be better than a preplumbed settup 1000 gallon+ tank? I figured I could build an acrylic box that closes in a column of water right over the foot space at the very bottom. Drill holes big enough in that for some small fish to get in and out and fill that center part with live rock for bio filtering. Put a deep sand bed at the bottom of that under the rock. Hand about for 250w MH lights near the center to get the rock pretty and let the sharks and rays have free reighn over the seating area.

Iv seen used working hot tubs for less than a grand that need exterior wood working. Which I do for a living anyway.

Now for the draw backs. Dont have a house where Im sure it would be perminent and who knows how many times within a hot tub system the water comes in contact with metals.

Maybe one day...