I'm thinking the main body where the farming happens, flowing into a portion that serves as a sump (algae and mangroves), spilling into a a return area where the water is pumped back to the other side. There have it waterfall over rocks for filtration/aeration into the main part again. That tail piece that goes into the return tank could double as a huge algae scrubber for added export.

Water changes, although may not be needed, should encourage you to plumb the system into the city system unless you like dead grass. Might want to check and see how much salt water is safe to dump without environmental concerns.

I'm thinking your ROI would be negligible to nonexistent.

As far as heating and cooling you may be better off building a greenhouse with AC. Then you can build the propagation tanks at a comfortable height. Ambient temp would regulate water temp. Still have the availability of solar energy for growth.

And the fact that mama won't have to deal with seeing what you're doing to her house you can safely build some elaborate scrubbers to keep your water pristine and maximize your water levels individually and at a low cost. Ie, tupleware containers for growth, shallow for sp requiring high heat and deep ones for those requiring the depth.

You won't have the expense of glass tanks.

You could build this close to the house and at a later date when you get your stones back you can pipe in a water supply to a display tank, run the return back outside and that would give you a 55gallon DT with a 1000 gallon fuge.

Most of us would salivate at that