A very unusual idea. Which is quite commendable (IMHO)! I am a champion sucker for anything unusual!
The flip side is you will run into many unusual and hard problems, especially combining a functional kitchen island counter with a functional monster fish tank.
It'd be much better to separate the two. If this is being thought of because of space savings, then I'd say you won't save as much space as you think as the filter and the air will have to be dropped into the basement or set up in the garage and the piping will take up some space, not to mention a can of worms of potential problems with installing and maintaining the piping.
The kitchen floor will have to be reinforced to a great extent or rather you may need pillars go into the basement and onto the house slab to hold up the weight.
You will have to waterproof the space above the tank / under the counter too.
You will not be pleased with the fish viewing too much either but 5' is still a decent size window.
You don't want to go over 1 cubic inch of fish body volume per 1 gallon of water no matter how large your water changes are... unless we are talking 100% WC per hour or two, which is pure fantasy for normal people.