In summary, the following is a flow for setting up an aquarium. Decide on the type of fish and the number. Review choice of flora and fauna. Determine size and type of aquarium. This is a very rough rule of thumb.
Tall fish look good in tall tanks.
A tall tank with a given surface area will support the SAME number of fish as a short tank with the same surface area. Each gallon of water weighs 8.5 pounds. Make sure your floor can support the weight. Also ensure a stable platform. Larger aquaria are subject to less fluctuation of temperature and water quality.