Changing aquarium water can be a simple and safe business. The easiest procedure is to transfer the fish in the old water into another container. Then clean the aquarium, refill it, and let it stand for two or three hours before you move the fish back into it. This allows the fresh water to approach proper temperature and also permits the release of any unnatural gases-an important consideration if you live in a community where water is heavily chlorinated.

As a short cut, when drawing new water for the fish, press your thumb against the tap so that the water comes out in a fine spray (or attach a spray gadget to your faucet). This aeration gets rid of chlorine. Then bring the water to proper temperature with a few cups from the hotwater tap.

The same procedure should be followed when changing water in an outdoor pool. Transfer the goldfish, in the old water, to some used wash tubs or other suitable vessels, and set them where sunlight will not fall directly on them. Normally, the greater amount of the pool water would require more time to warm up and release chlorine, but the same short cut can be used. Fill the pool with the nozzle of the garden hose adjusted to throw a spray. Filling of the pool this way may take a little longer, but the aerating of the water is worth the extra time. As for temperature, warm up the water with a few buckets of hot water.

Take care as to the kind of container you select to hold the fish while the pool is being refilled. New wooden tubs (unless of white cedar or cypress) and new zinc tubs may poison fish, as will any kind of container made of copper. A well-used zinc washtub, a crock, or stone jar will do very well.

Many an interested amateur might have installed an aquarium of goldfish in the living room long ago if he had not been frightened by the idea that it entails a lot of expense, particularly the cost of an air pump which he has been told is necessary. Not so. Air pumps are used advantageously by pet-store operators who must crowd a lot of fish into limited quarters. Such pumps, however, certainly are not necessary for aquariums that are not overcrowded. Follow the capacity rule in stocking an aquarium, add a few oxygenating plants, place the aquarium where it can get the required sunlight, and you will have no need for a pump. Neither will you need a trickle of running water, another petstore device. In fact, either an air pump or running water can keep in constant turmoil an aquarium which otherwise would soon become well balanced.