Ideally, an aquarium should be placed where there is two hours of direct sunlight daily. This much light playing upon the oxygenating plants will enable them to do their good work efficiently, and yet it is not enough to make the water dangerously warm.

Sunlight is harmful if it causes too much plant action in the aquarium, resulting in an overabundance of algae and other microscopic green growth. This can be controlled to an extent by smearing the sunny side of an aquarium (on the outside) with a coating of Bon Ami or other household cleanser. If this doesn't check excess growth, try covering the sunny side of the aquarium with colored cellophane or with colored or white paper.

As for sunlight on the outdoor pool, a minimum of four hours day was or should have been-one of the prerequisites for the pool site. The more sun above and beyond this minimum, the better.

An insidious cause of death among goldfish is shock, the effect of which is often not noticeable right away. Just as a bad cold or extreme fatigue can weaken the resistance of a human being and make him susceptible to various ills that he might be strong enough to resist otherwise, so shock weakens goldfish.

They suffer shock most often while being transferred from the pet store to their new home, or while the pool or aquarium water is being changed. The shock in the first instance is slight and necessary; in the second instance, it is unnecessary and can be fatal. When you clean an aquarium, don't draw a bucket or huge jar of cold water from the tap, gather the goldfish in a net, dump them into it, and leave them there for two or three hours while you scrub and refill the aquarium, and then dump the fish back into fresh, clean, cold water. This is shocking treatment because it is completely different from anything fish might encounter under natural conditions. For fish, there is no such thing as a sudden natural change. Air temperature may soar or drop alarmingly, to the intense discomfort of human beings and other air-breathing animals, but change of environment for fish is always very gradual.

Fish subjected to such shock probably won't show the il1 effects immediately. A day or two afterwards, however, a dozen different goldfish may display a dozen different ailments, all results of shock-sluggishness, congested fins and tails, a dull, filmy covering on the scales, and so on. Most of them will probably recover in time, particularly if doctored. Such continued shocks, however, wil1 keep them in poor condition, and drastically reduce their normal lifespan.