This shape is technically a hexagon, seeing as there are 6 sides.
A tank shaped stand would have a leg at every corner. to make it look good you're going to need a compound miter saw (and probably a table saw) to cut the 45 degree angles.
If your 'shop' consists of Home Depot cutting your lumber for you, make a big rectangle stand and have a corner to put your beverage while you admire your fish.