Have you noticed that the water in your aquarium has suddenly become cloudy and taken on an unpleasant green tint? Most likely, you are dealing with what is known as “water blooming.” This is a common problem that can ruin the appearance of any aquarium.
The reason for this phenomenon is simple: microscopic algae begin to actively multiply in the water. They are so small that they float in the water column rather than growing on the walls or decorations. This makes the water look like green “soup” and it is almost impossible to see through it.
The good news is that this often does not pose a serious danger to fish. The bad news is that such water looks very unaesthetic and signals an imbalance in your aquarium. Let's figure out why this happens and how to restore crystal clarity to the water.
Green water in an aquarium is not a disease, but simply an overgrowth of algae that makes the water cloudy and green. This is most often caused by overly bright light and an excess of nutrients, especially if the aquarium is placed in direct sunlight or the light is left on longer than necessary. The solution is simple: reduce the lighting time, do not overfeed the fish, change the water, and give beneficial bacteria and plants a chance to restore order. Sometimes an ultraviolet sterilizer or the addition of live crustaceans helps. The main thing is not to panic; this is a common and completely fixable situation.
Reasons for its appearance
Algae spores are constantly circulating in the atmosphere and can easily be carried into the aquarium. In small, invisible quantities, they are usually already present in aquarium water.
The sudden appearance of floating algae can be caused by seasonal changes in water composition, increased temperature and light levels, which are most pronounced in spring and summer.
However, these factors cannot cause “water blooming” in the absence of nutrients.
In hobbyist aquariums, excess nutrients are often associated with the accumulation of organic matter. This includes the decomposition of plant fragments, uneaten food, fish excrement, etc. Favorable conditions for the growth of microscopic algae arise when nitrate concentrations begin to exceed 25 mg/L.
This situation is typical for aquariums that are not regularly maintained or in new tanks with an unstable nitrogen cycle.
Thus, the main cause of green water in an aquarium is an excess of nutrients combined with high light intensity.
How to prevent “water blooming” in an aquarium
Solving the problem of “water blooming” begins with identifying the causes. If the aquarium is located close to a window and/or is exposed to direct sunlight, it makes sense to change its location.
Excess nutrients are removed by replacing part of the water with fresh water on a weekly basis, which should be done together with cleaning the substrate of accumulated organic matter.
It is important to regularly maintain the filtration system. In a situation of “water blooming,” the filter experiences an increased load, as a significant portion of the algae settles in it. The filter material must be washed gently, preferably in a separate tank with water from the aquarium, to minimize the death of beneficial nitrifying bacteria.
How to get rid of green water in an aquarium
If preventive measures are too late and the water has turned green, there are several effective ways to get rid of algae.
Method #1. Use additional filter elements.
Some of the algae can be collected using foam rubber, a sponge, or any other fine-pored material, attaching it to the filter's water intake. The material should be replaced or thoroughly washed periodically.
This measure is temporary. Although it reduces the accumulation of plant debris in the filter itself, additional external materials significantly impair the performance of the filtration system due to the inevitable reduction in water suction power.
Method #2. Use of water sterilizers
The most popular method is ultraviolet water treatment. UV sterilizers can be built into the filtration system or supplied as separate devices. The most common are stand-alone devices, which are hollow cylinders with a UV lamp or UV LEDs inside. The ends of the device are equipped with connectors that allow it to be connected to the pipes of an external filter or a separate pump. The pump or filter ensures that water from the aquarium passes through the ultraviolet lamp or LEDs installed inside the sterilizer.
Ultraviolet light is effective not only against algae, but also removes most pathogenic microorganisms circulating in the water.
A relatively new type of sterilizer on the European market was introduced by Twinstar in 2012. The device was presented as a high-tech product. Its principle of operation is based on direct water electrolysis.
In aquarium water with many dissolved substances, various reactions occur during electrolysis, releasing ozone, hydrogen peroxide, oxygen, sodium hypochlorite, etc. It is sodium hypochlorite that has the necessary antiseptic and disinfecting effect.
The Twinstar device and its analogues can be considered as a means of combating algae. However, it is not a panacea and is only effective in the early stages or as a preventive measure. The effect in a heavily infected aquarium will be minimal.
Method #3. Darkening the aquarium
If there are no live plants in the aquarium, an effective remedy for green water is to darken the aquarium. The tank is completely covered from light and the lighting is turned off (the filter should continue to work). Deprived of light, photosynthetic algae die within 7 days.
However, the aquarium can be affected not only by algae, but also by single-celled organisms.
Euglena
(“Euglena” in Russian transcription). For a long time, they were classified as algae, but later studies identified them as a genus of single-celled flagellate eukaryotes. This organism contains chloroplasts like plants and can feed on the sun's energy. But Euglena can also feed heterotrophically, like animals, by eating bacteria.
If darkening the aquarium does not help, it means that it is affected by Euglena, and in this case, you need to resort to methods #1, #2, #5, and possibly #4.
So, green water is not a death sentence for your aquarium. It is just a sign that too many microscopic algae that love excess light and nutrients have settled in it.
The most important thing is not to panic and not to start a total war with the entire contents of the tank. Abruptly replacing all the water or turning off the filter will only aggravate the situation. You need to act calmly and consistently.
Remember what we discussed: reduce daylight hours, check that you are not overfeeding your fish, and remove excess organic debris. A simple UV sterilizer or a more powerful filter may help. The main thing is to find and eliminate the cause of the excess “food” for the algae.
Be patient. Restoring biological balance is not an instant process. But when the water becomes crystal clear again, you will know for sure that your underwater world is back in order. Aquarium keeping is all about this gradual restoration of harmony.
