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.