The size of your collection will depend on the size of the container.

Your aquarium should be carefully washed in lots of clean water (soap or detergents would be harmful to the animals you will put in it). Then let your container sit full of clean water for several days for the water to absorb any remaining impurities. Pour this water out. Place the container in a permanent location where it will get at least two hours of direct sun (morning or afternoon) each day, and begin to reproduce the habitat of the animals you have decided to collect. In collecting animals for an aquarium, remember that you cannot keep animals from different habitats in the same aquarium. Your aquarium must reproduce only one habitat.

To collect animals for your aquarium you will need a net for scooping animals out of water, a piece of screen for screening very small animals out of the water (optional), a fine meshed basket with a handle attached to scoop animals out of the water (optional), and glass or plastic containers to hold the animals in their water. A non-metalic tray would be helpful for sorting and choosing the animals you will keep. Any animal that you don't want should be returned to the water. Remember the size of your container as you are collecting. For a small container, several small animals are more interesting than one large one. Do not over-populate your container space; if you want variety you can change your collection frequently.