Question: I'm cheesed off with my tank: the water gets green and another time - brown. Tired of renewing aquatic plants.
Answer: Not only the fish get ill, but the plants and water as well.
Reason 1. In summer when the light is too bright and the temperature high the water may get green. This is the result of mass reproduction of microscopic algae, mostly Euglena. Sometimes other tiny harmful algae cause white-green haze in the water. These algae also develop at the bright light. If the blooming hasn't gone too far, it doesn't do much harm to the fish, unless the fish got into such water suddenly.
To reduce the blossom make a shade over your aquarium, e.g. cover it with a light-tight cloth. Keep the tank so until the water is clean. The second tested way to get rid of blooming is to put alive Daphnia in the tank: so many as the fish don't eat them up very quickly. Water fleas eliminate algae: they feed on them. Usually one day is enough for them to make the water crystal-clear. It goes without saying that the method with Daphnia is possible only when the tank is not overpopulated. Otherwise oxygen deficiency may lead to the fleas' death and enhance of water spoiling.
To avoid water blossom cover the sunny wall with sparse gauze or a sheet of thin white paper.
Reason 2. Sometimes the water gets green because a great amount of organic deposits accumulate at the bottom. Remove them at first.
Green algae on walls, under water equipment and plants are usually harmless. As a rule, it is enough just to clean the glass wall with a scraper. In order to reduce the amount of such deposits on plants and media you may: (1) settle special kinds of fish into the tank, for instance some species of Pupfishes (Cyprinodontidae) eat the algae; (2) temporally shade the aquarium; (3) replace the bulbs with other, less powerful.
Reason 3. When the equipment and plants get covered with brown algae, this most likely happen when lighting is insufficient. Usually brown algae show up in winter within the tanks which are kept without artificial lighting. In such aquariums plants feel bad too. Their leaves lose color, become yellow, thin and flabby, and start to decay.
Treat the ill plants and remove brown algae by settling the tank at some alight place. The best remedy is installing artificial lighting above water.
Reason 4. The worst enemy is cyanobacteria. They reproduce extreme quickly, form a stinking coating on leaves and stems of aquatic plants and thus inhibit their growth and total activity. The way to fight them is as such. Use a scraper to clean glass and plastic parts. Carefully remove algae coating from the plants leaves with your fingers. Remove dirt that accumulated during cleaning at the bottom of the tank by means of a tube coil. In addition loosen the substrate and put algae-eaters into aquarium (give them ordinary food a little less than usually).
Reason 5. Beside the described troublemakers one can sometimes see hair algae that live on the alight walls of a tank. If they are too much, they can become a dangerous trap for small-sized fish.
Fight hair algae with the following method: reduce amount of light in the tank and place many ramshorn snails or kinds of fish that readily eat hair algae. For a warm water aquarium these are mollies. Other livebearers eat them too, but not so eagerly. For a cold water tank use rudds and bitterlings. Interestingly, when there are some mollies in the tank other kinds of fish imitate them and begin to feed on algae.
By Lyudmila Stushkovskaya. 1000 advices about how to treat pets
Translated by Tatiana Karpova (Moscow)
(MSU, Biology faculture, Dep. zoology and ecology).