Suzie Newman, age 10, of San Bernardino, California, for her question:

How does a goldfish put her eggs on the underside of a lily pad?

It would, of course, be rather risky to leave those precious eggs on the top of a lily pad. Out in plain sight, they would be spotted and gobbled up by birds and bugs, frogs and other hungry enemies. They are safer on the underside of the leaf  but placing them there poses a problem.

A mother goldfish solves this problem without instruction. When she is almost ready to lay her eggs, she selects the shady underside of a lily pad. If there is no lily pad in her pool, she chooses the widest waterweed she can find. Then she sets about cleaning a spot, the very spot where she intends to place her eggs. She does this job with her mouth, nibbling and nozzling until the underside of the leaf is clean of algae, slime and other dirty debris.

Mr. Goldfish, by the way, is nearby supervising operations. This is very important, for later he has a duty to perform and without his help, all Mrs. Goldfish's nursery activity would come to nothing. When the cleaning job is done, the papa fish is not surprised to see the little mother turn herself upside down. In this position, she swims around and places her eggs one by one right in the middle of the cleaned patch on the underside of the lily pad. They do not fall off because the eggs happen to be covered with an adhesive material. When placed on the leaf, there they stick.

Now her work is done and it is Mr. Goldfish's turn to keep his part of the bargain. The eggs laid by the female are unfertilized. The male fish swims over them, often several times, spraying them with sperm cells, many of which find their ways to egg cells. These merge and each pair forms one fertilized egg. Both parents then swim off and forget all about their little brood.

There may be 20 eggs in the batch and, if all goes well, they hatch in about a week. The infants are tiny, dark wrigglers and even their parents do not recognize them as their own. In fact, adult goldfish often snap at their young and even devour them. For this reason, now is the time to make a few changes in your goldfish aquarium. Remove the parents to another home until the youngsters are at least one inch long. If you know when the eggs are laid, it is better to remove the adult fish right then, in case the brood hatches and comes to grief during your absence.

The female goldfish may lay brood after brood and produce perhaps 500 eggs during the summer season. The first batch hatches in April or May, depending upon the weather. Goldfish may be harmed by sharp changes in temperature and if you keep them indoors, remember that they prefer the water in their tanks to remain around 65 or 70 degrees Fahrenheit. Feed them once each day. And either clean out the algae from the water or add a few water snails to do this job for you.

There are several reasons why a goldfish tank should contain tufts of waterweeds. The greenery produces oxygen for the fish to breathe. It provides shade for the fishes. It changes a tank into an aquarium, just by making it decorative. And, just in case a female goldfish should decide to lay a batch of her little eggs, the underside of a wide leaf of waterweed provides just the right nursery for them.