One of the major advantages of studying the ecosystems within a pond community is that you can capture different life forms and keep them in your classroom by setting up a pond community aquarium. An aquarium is one of the most fascinating nature projects because a large variety of pond animals can be maintained in captivity with a minimum amount of care and equipment. Keeping these animals in your classroom, under conditions approximating their natural habitat, will give students the opportunity of studying them at close range and in detail. However, the main problem with an aquarium is to see that it is balanced. This means that the animals, which give off carbon dioxide into the water, must be balanced with the plant life, which produce the oxygen in the tank for the animals to survive.
Before your trip to an actual pond, there are several things that must be done to the aquarium in order for it to be ready for the specimen that your class collects. The aquarium should be washed out thoroughly with clean, clear water. The gravel should be rinsed several times with clear water in a colander, this is to assure that the small rocks are free of any debris. If you choose to use the underwater filtration system (highly recommended), this should be rinsed and place in the bottom of the cleaned aquarium. Then the tubing should be placed in the aquarium along with the diffuser or airstone. Place the aquarium where you plan to keep it upon your return from the pond because once the water is added it will be too heavy to move. Direct sunlight is not necessary for the aquarium; the light from a north window is ideal. If the aquarium water becomes green from algae growth, cut down on the amount of light entering the aquarium by masking the sides towards the window with paper or paint. Since ponds are relatively cool anyway, a minimal amount of sunlight is needed. Now you are ready to take your trip to the pond. (See lesson plans at the end of the unit titled—”Visiting A Pond Community”—for preparatory notes for the trip.
Once you return to your classroom with the specimen collected from the pond, there are several steps that you should follow in placing the specimen in the aquarium. Fill about two-thirds of the aquarium with the pond water you collected. Then place the plants in the water. If some of the plants collected contain roots, advise the students to make sure they place the roots under the gravel. Other plants can be allowed to float or can be anchored underneath a rock. If the pond you visited was too deep for the children to get to the underwater plants, they can be purchased from a pet shop. Some of the possible plants that you can purchase to put in your pond aquarium are—Cabomba, Vallisneria, Anacharis, Nitella, Lemna, or Elodea.
The animals that your class collected should be added to the aquarium next. Some of the animal life collected should include-pond snails, crayfish, newts, tadpoles, water insects. Small fishes should also be included, but you must be careful not to overcrowd the fish. One inch of fish (not including the tail) per gallon of water is a good rule to follow. If the students collected some of the smaller animals such as daphnias or water fleas, they should be added to the tank also because they provide food for the larger animals. As the tadpoles develop into frogs, make sure they have some type of floating platform in the aquarium so that they may come out of the water. Once the tadpole has become a frog you may want to let it go, or place it into a second aquarium.
In the introductory notes, I suggested setting up two aquariums because if your class collects turtles, frogs or salamanders because they should not be totally submerged underwater. If reptiles are collected, your class should set up the second aquarium like a terrarium. Make sure that there is a small area set aside in the aquarium like a pond so that the reptiles can keep their body moist. Rocks should be used to provide an area assimilating land for the animals. Also make sure that there is a variety of plant life in the terrarium for the animals as to provide some type of shelter or privacy for the reptiles.
Plant-eating animals (herbivores) such as fish, snails and tadpoles will nibble on the plants growing in the tank, but you may add a few pieces of spinach or lettuce to supplement their diets. Animal-eaters can feed on daphnias, small worms and insects, or in the case of fishes, prepared fish foods purchased from a pet shop.