I would probably look into buying a house in our town that was on the market briefly last year. I think it may have been taken off the market because there were too many gawkers, or the owner just couldn't bring themselves to part with the sharks and rays...
A guy in our town is a big-time creator of gambling software for slot machines (I think he created the wheel of fortune slots for those who are familiar with them), has made millions. I'd heard about him building a house "around" a big aquarium back in the 90's, finally saw pictures of it during the 2 months it was listed last fall. When you google worlds largest home aquarium, you won't find his, but you will find some smaller diy tanks in the 10-20K gallon range. Unfortunately all of the images are gone since they removed the listing or I'd link them.
The dude has a 25 foot wide, 10 foot high cylinder tank in his barn/mancave/private office. The thing is amazing, black tip reef sharks, sting rays, etc. My guess is the aquarium is almost worth what he was asking for the house at the time. I'd relocate to that property in a heartbeat.