An aquarium provides a useful and interesting teaching aid for the  classroom. Students observe growth and development of plant and animal  life, community relationships, feeding habits, and predator-prey  relationships. The design should be a biosphere in which plants and  animals survive and grow with little care. 
Each classroom is different; therefore, the following requirements need  to be considered before finding a permanent location for the aquarium.  Avoid wide-range fluctuations in light and temperature. Natural light  may be controlled by blinds or shades at the windows. To reduce the rate  of evaporation and sudden temperature changes, do not place the  aquarium in a direct airflow from a heater or air conditioning duct.  Artificial light may be used. In the interest of safety, consider the  traffic pattern in the classroom. 
The aquarium needs to be thoroughly rinsed with water. NEVER USE SOAP in  an aquarium. Soap is difficult to rinse out, and any residue can kill  the organisms. To remove water marks or mineral deposits on the glass,  apply towels soaked in vinegar. Rinse with water afterwards. Fill the  aquarium with water and check for leaks. A small leak may seal itself by  the weight of the water pressing on the glass. If a leak persists, the  aquarium must be emptied, dried, and sealed with silicon cement or  aquarium sealer. After the water is added to the aquarium, it must be  aged for a week. The ideal water temperature is between 65 to 75°F. The  aquarium may be covered by a piece of glass, Plexiglas, or plastic wrap  to reduce evaporation or airborne contamination. Care must be taken not  to seal tightly and restrict the air exchange. 
The aquarium may be covered with a 2-inch layer of small gravel. Any  gravel or rocks must be thoroughly washed prior to adding them to the  aquarium. 
Plants - Plants provide a cover for small fish, remove nitrogenous waste  released by animals, and absorb carbon dioxide. The primary  considerations in the choice of plants are based on the light conditions  and the size of the aquarium. Elodea, duckweed, and Vallisneria require  high light conditions. Chara (a stonewort) and Vesicularia (an aquatic  moss) do well in low light. Duckweed and Vallisneria are best suited to  aquariums 10 gallons or larger. Elodea, Chara, and Vesicularia may be  floated on the surface or rooted in the gravel. Vallisneria needs to be  rooted in the gravel. Duckweed is a floating plant that multiples  rapidly. Harvest (remove) some of the duckweed whenever it covers the  surface of the water so that it will not restrict light and gas  exchange. 
Animals - After a week, aquatic animals may be added to the aquarium.  Allow 3 inches of fish (vertebrates) body-length per each one gallon of  water. Float the bag of fish in the water of the aquarium for 20 minutes  before adding the fish to the aquarium to reduce stress on the fish.  Snails (invertebrates) add interest to the aquarium. In the spring frog  eggs, tadpoles, or salamanders may be found in nature. Unless you are  able to classify these organisms to determine their dietary  requirements, practice sound environmental procedures and leave them  undisturbed. Hydra and daphnia may be added to demonstrate specific food  chains or predator-prey relationships. 
Check the aquarium daily for dead animals or plants. Remove accumulated  waste from the bottom once a month. Replace one-third of the water each  month with aged water. Feed animals at regular intervals, never feeding  more food than can be consumed in 30 minutes. Remove the remaining food  to reduce a build-up of organic wastes, which clouds the water and  lowers oxygen concentration. Flake food available at pet centers is a  good basic diet. Brine shrimp eggs may be hatched, rinsed in fresh  water, and fed to fish and invertebrates.
 
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