A fish bowl can be used to make an artificial home for pond animals, but a glass container with straight sides is better, because you cannot see the animals as they actually are when you look at them through curved glass. The rectangular aquarium which is sketched at the beginning of this chapter was purchased from the local gold­fish dealer for a dollar. It served very well for the vegetarians collected. It was found best to keep the carnivorous animals in separate containers.

The bottom of the aquarium should be covered with a layer of clean sand. Remem­ber that you are trying to make a small model of the pond from which the animals came. Transplant some pond weed or other water plants to the sand to help keep the water fresh. Plants need oxygen, just as animals do, but plants also produce oxygen when they manufacture their food. The extra oxygen which comes from the plants will help keep your aquarium animals alive. The simple plants called algae, which grow in ponds and ditches, may be used, but you will have a more attractive aquarium if any of the leafy plants which grow in or under water are used. You will also find it easier to watch the activities of the animals than if the open water is filled with floating algae. A few snails are essential to every aquarium, for they help to keep it clean.

You may prefer to have several small aquaria rather than one large aquarium. In this way you can keep the larger animals from killing the weaker ones. You will also be able to make a closer study of some of the animals if they are separate. A reading glass can be held in the water to enlarge the animals while studying them.