How to Prevent Algae from Growing in Your Tropical Aquarium?

It is best to eliminate “green water” before the growth becomes too heavy. Usually this can be done by cutting down the amount of light. This dimming of the light should be done gradually. Cutting off all the light at once can cause the algae to die suddenly, with the resultant of decomposition.

Placing a large quantity of Daphnia (small water crustaceans), which feed on “green water,” in the tank for a few days will also usually clear it up. However, the fishes must be removed or they will eat the Daphnia. They can be replaced to clear up the Daphnia after the latter have done their job.

Fresh-water mussels will also eliminate “green water.” The difficulty is that once they have done the job, they may starve to death and pollute the tank. The quickest method is to dissolve one grain of potassium permanganate by weight to every gallon of aquarium water. This turns the water pink or brown but clears it in a few days. This treatment is also effective for a grayish cloud caused by excess bacterial activity. If the fishes show any distress by hanging at the surface of the water after treatment, change one-third to one-half of the water.

Keeping an aquarium clean will help control algae by depriving them of one of their basic foods - the CO2 caused by decomposition.

Changing all or part of the water is worse than useless. Fresh water acts as a stimulant and actually increases the growth of algae.

The other algae are thread algae, blanket algae, and filament algae which will all yield to decreased light. Siphoning can remove much of the blanket algae. Plecostomus catfish and snails will eat the filamentous types. A fork can be used to entangle and uproot thread algae, while a stiff brush will remove it from rocks and ornaments.

Should ornamental rocks or other ornaments be used?

Let taste be your guide when coming to decide whether ornamental rocks or other ornaments be used. Today many aquarium stores feature rocks of all types, as well as glass chunks. Many of these have sharp edges, but there is little reason to believe that the fishes ever cut themselves on them. Mineral or lime-bearing rocks, of course, should be avoided.

When in doubt as to the danger of a particular rock or type of rock, test it first, placing it in a tank with a few inexpensive fishes for about two weeks. Rocks serve no particular purpose in the community aquarium (unless it’s a community of African cichlids), but many of them are decorative and can be arranged into caves, grottoes, ledges and walls within which or on which some fishes will spawn.

Almost the same could be said of other aquarium ornaments. Bamboo huts, castles, bridges, figurines, frogs, treasure chests, turtles, etc., are available. If you like them and their material and style does no harm, use them to beautify your aquarium.

A word of caution: be sure that all the rocks and ornaments used are set well into the gravel. Do not leave areas under which dirt can drift and accumulate beyond reach. Make sure that such areas do not exist in the ornament itself. And beware of the ornament that has narrow, closed-end passageways. A fish is quite likely to swim up into it and, being unable either to turn or proceed, to die there. Not only will you lose the fish, but its body is likely to be hidden and can pollute the water before being discovered. Many seashells fall into this category.

Coral as well as seashells is composed of lime. A small piece or two of coral or a few small shells probably do no harm. In excess, they certainly tend to make the water hard, if it is originally of the soft, slightly acid type. Coral and seashells should be boiled and scrubbed thoroughly with a stiff brush before use.