[header] How to decorate a fish tank [title] Try a colorful sand for a beautiful base. [step] Aquarium sand and comes in a variety of colors, and you can choose your favorite as a base for your aquarium. Light colors do well, as they become almost glittery in water. 
You can also layer different colors, though keep in mind they will get mixed up over time. [substeps] Another option is a pale tan sand to make your aquarium look like the ocean.