I would make the tank 72" long x12" deep x18" tall
narrow but the full rear span but taller and narrower so you can still get a tang or two in there.
make the desk 18" deep and 72" long and use a laptop as your computer. Make the above tank cabinets the full ceiling height or just go with an open concept system like in the pictures you had above.
I would tape out a 3'x2' square on your dining table to get a feel for that size of desk. Its pretty small and you wont be able to spread out a couple books or what not when you need to do some "real" work
. I just roughed it out myself and i felt like i was in grade school again, lol.