Measure both the length and the width of your aquarium. You should design your stand to be large enough for the aquarium to squarely fit on the stand's surface without the aquarium edges extending over the sides.
Select a material for your stand. Pine works well, but depending on your room decor, you might choose white oak with a walnut stain, maple with a cherry finish, or any other combination. Select a wood and a finish that fits your tastes.
Research the filled weight of your aquarium. Consult your aquarium's instructions for this information. A small tank (15 gallons, 20 by 10 by 18 inches) will have a filled weight of approximately 170 lbs. A medium tank (29 gallons, 30 by 12 by 18 inches) ends up around 330 lbs. A large tank (150 gallons, 72 by 18 by 28 inches) weighs an impressive 1800 lbs. The stand described in this article is not recommended for any tank heavier than 500 lbs.
Measure the height at which you would like the aquarium to sit. Keep in mind your need to reach the top of the aquarium regularly for feeding and cleaning.
Subtract 5/8 inch from the overall height you desire. Cut four legs to that length. The legs should be made of stock measuring at least 1 1/2 by 1 1/2 inch. If you have a lathe and can turn the legs into a fashionable design, the extra effort will make the stand look fancy. Using a table saw, cut the stand's surface piece from your 5/8-inch board. Use the dimensions determined in Step 1.
Lay out where you want the legs to be positioned. Ideally the stand's surface should overhang the legs by at least two inches on all sides. Once the leg positions are marked on the underside of the stand's surface, measure the distance between them. A stabilizing piece of wood measuring at least 1 inch by 3 inches should be cut for all four sides. If desired, you may lay out a decorative pattern for these pieces and cut with a scroll saw.
Drill peg holes into both the stand legs and the stabilizing 1-by-3-inch stock. Apply wood glue to holes and insert pegs cut from the 1/4-inch dowel. Clamp and allow to set. Use the same glue-and-peg method to attach the stand's surface to the legs.
Sand your stand. Begin with 60 grit before progressing to 80 and 120 grit papers. Once the entire stand has been sanded with all three grits, stain and lacquer your stand, or paint it if you choose. If you choose to stain and lacquer, you may want to follow the first coat of lacquer with a light sanding with 120 grit, before applying a second coat of lacquer.