Keeping Freshwater Tropical Fish

One of the most important requirements for keeping fish healthy and attractive is clean water in sufficient quantities to provide them with adequate amounts of oxygen and freedom of movement. An aquarium should be rectangular in shape. A goldfish bowl does not allow for enough water surface for adequate absorption of oxygen and release of carbon dioxide and other gases poisonous to fish.

Oxygen consumption varies greatly according to the age, size, and species of fish. However, a good general rule for an aquarium not equipped with an aerator is that there should be one gallon of water and 24 square inches of water surface for each inch of fish exclusive of tail. (In metric units, this is 1.5 liters of water and 60 cm2 of water surface for each centimeter of fish.) When an aerator is used, about half as much water volume and surface is needed. If the aquarium is properly cared for, the water need never be changed.

The aquarium should be placed out of direct sunlight during most of the day to prevent the growth of algae, which are harmful to freshwater tropical fish. It should not stand in a draft or near a room heater. Suitable water temperatures for most tropical fish range from 70° F. to 80° F. (21° to 27° C.). The fish should never be subjected to sudden changes of temperature.

Aquarists who breed fish usually have a second tank for spawning and keeping the young, because adult fish often eat the young, even their own. Peaceable fish of the same approximate size can be grouped together. Aggressive kinds must be kept alone or with their own species.

A variety of feed can be bought in pet shops. Dry prepared feed consisting of a combination of fish and shellfish meal, beef meal, and plant material is excellent. In addition, fish should be given such live feed as daphnia, brine shrimp, white worms, tubifex worms, and certain water protozoans. Animal and vegetable material prepared by freeze-drying (drying frozen material in a vacuum) may sometimes be substituted for live food. Chopped fish, liver, and earthworms are good fish feed. Fish do not overeat, but they should not be given more feed than they can eat in 15 or 20 minutes, because uneaten particles decay and stimulate the growth of harmful bacteria.

Fungus diseases and white spot (or ich), caused by protozoans, are the most common diseases affecting tropical fish. Treatment usually consists of adding chemicals to the aquarium water. Afflicted freshwater fish often benefit from being placed in a weak saltwater solution for several hours. Diseases can often be prevented if newly acquired fish are placed in a tank filled with a solution of potassium permanganate for a few hours before being put in with the other fish.