Aquariums

Aquariums are now very popular in homes. Many kinds of fishes can be kept successfully in them. The secret of having a good aquarium is to have an aquarium tank that is large enough for the number of fish one plans to keep, to have plenty of green plants in it, and to have enough snails or other scavengers to keep the aquarium clean.

If there are plenty of green plants and scavengers, the water does not have to be changed often. The plants are important because, when they are in sunlight, they use up carbon dioxide and throw away oxygen. Fish like all animals, are constantly using up oxygen and throwing away carbon dioxide. Plants in the water help to keep it fit for the fish by keeping the carbon dioxide content low and the oxygen content high.

Among the most popular fishes for aquariums now are tropical fishes such as guppies, swordtails, angelfish, and zebra fish. They are small, interestingly colored, and fun to watch. Many of these tiny tropical fishes are live bearing. The female, that is, keeps the eggs in her body until the young develop from them. One problem in raising these tiny live-bearing fishes is to keep the adult fishes from eating up the young. An aquarium for live-bearing fishes should have plenty of plants to afford hiding places. Keeping the water warm enough during the winter months and providing the right kind of food will keep these tropical fishes healthy and happy.

The goldfish is by far the most popular of all our aquarium fishes. Goldfish may now be bought in a great variety of colors. They may be bought with bulging “telescope” eyes and with very long, flowing tails. They may be bought with scales or without. The story of the goldfish is a story of man’s ability gradually to change the animals he has domesticated.

All the goldfish of today are descendants of the wild goldfish that live in the streams of China and Japan. This wild goldfish is not an especially pretty fish. It is usually dull green, and it has small fins and a rather short tail. The Chinese found out centuries ago that it is easy to raise goldfish in small ponds and aquariums. Many kinds of fish do not do well in captivity, but the goldfish does. The Chinese found out, too, that not all goldfish are alike in color. Occasionally they found a fish that had the green color left out of its skin in places. In those places the skin was yellow or gold.

The Chinese watched carefully for fish with a gold color. They took good care of these fish and their eggs. Some of the fish that came from the eggs had more gold color than their parents. The Chinese breeders kept on choosing and mating the fish that were the best. In time they had fish that were all gold.

At least 400 years ago the Japanese, too, began raising goldfish. Goldfish breeders soon found that they could produce goldfish that were neither green nor gold. Now we have black goldfish, silver goldfish and goldfish as spotted as a tortoise-shell cat.