Forest Preserve District of Cook County, Illinois
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School Aquariums
Nature Bulletin No. 577  October 24, 1959
Forest Preserve District of Cook County
Daniel Ryan, President
Roberts Mann, Conservation Editor
David H. Thompson, Senior Naturalist

Everybody seems to be born with a special curiosity about animals that live in water. Partly, this is because the underwater world is so different from our life on land partly because aquatic animals are of so many strange kinds or are so secretive that they are "sights unseen" to most people.

The best way to get better acquainted with many of the smaller ones is to catch, in a pond or stream, some small fish, tadpoles, crayfish, snails, or any of a wide variety of water insects. Carry them back home or to school in a bucket of water. Then they can be put in glass containers where they can be kept alive, their habits watched, and their life histories studied.

A wide variety of containers are suitable for aquariums, depending on the amount of money and space available. They may be rectangular tanks with glass sides and covers, ranging from two to ten gallons in capacity, or even larger. They may be wide-mouthed gallon jars, battery jars, fruit or mayonnaise jars. All containers should be thoroughly cleaned and rinsed before using. Enough coarse sand or gravel is needed to cover the bottoms of the tanks and a few of the jars to a depth of one or two inches. Previously, this should be washed repeatedly in running water until it is free from sediment and debris. This gives a natural background and an anchorage for a few water plants. A handful of pond mud and water-logged leaves in another jar often develops a wealth of microscopic life.

Clear pond water is best for native aquatic animals. If this is not possible, use tap water which has been exposed to the air in open containers for a day or more to allow oxygen to dissolve and chlorine to evaporate. Aquariums placed in a north window, or in diffuse light, thrive best. Direct sunlight for more than short periods is likely to overheat the water and stimulate objectionable growths of algae. Unlike tropical fish, which must be kept warm, our native water life is accustomed to winter cold and lives well in school buildings when the heat is turned down over week ends and holidays.

Beginners often overcrowd their aquariums. Too many animals are almost certain to exhaust the small amount of oxygen which can be dissolved in water, causing all of them to suffocate. A good rule is to allow no more than one inch of fish to each gallon of water. Thus, a 5- gallon tank can support only two 2 to 3-inch sunfish, bullheads or minnows. Plants should be used sparingly because, although they produce oxygen in light, they also use oxygen in darkness.

Crayfish, unless very small, prey on other aquarium animals and must be kept in a separate container, preferably in less than an inch of water with gravel heaped on one side where they can crawl out occasionally. They are primarily carnivorous and can be fed small earthworms or bits of hamburger.

Overfeeding is a common mistake. Sunfish and bullheads can be fed small earthworms, insects or bits of hamburger but they should be given only as much as they will clean up on the spot. Uneaten food spoils, fouls the water, and uses up the oxygen, causing animal life to smother. Pond snails and frog or toad-tadpoles eat plant materials -- bits of lettuce leaf, algae and sediment. Most of the larger aquatic insects, especially the adults and young of many kinds of water beetles and water bugs, are predacious, taking only live food, and must be kept by themselves. Live food can be caught for them by sweeping a smallmeshed dipnet through submerged trash and vegetation in ponds.

Of all schoolroom aquarium demonstrations, the most dramatic is the day-by-day development of frog or toad eggs inside their protective jelly.

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