Since we need to have an aquarium for goldfish, we will make a simple aquarium. Almost any clean glass container works quite well. If the container is round, like a jar, it may distort the appearance of the fish when we look through the sides. It depends upon the way the container was made.

The container should be of such size that the surface of the water should allow 20 square inches for each inch of the fishes' body length. That means that if we have three fish, one being two inches long, one being one inch long, and the third being two and 1/2 inches long, we have 5 1/2 inches of fish-body (this does not include fins), and we need 110 square inches of air surface to make certain that the fish will have enough oxygen.

Set the container in a strong light, but not in direct sunlight, because that would not only cause too much algae to grow inside the aquarium, it could heat the water to such a degree that the fish would die. We need to put 1 or 2 inches of clean sand mixed with gravel onto the floor of the aquarium.

We can go to the pet store and buy some plants to set into the sand and gravel floor, fish food, and some fish. Goldfish, guppies, and mollies do quite well in simple aquaria.