Algae in the Aquarium: Types, Causes and How They Are Eliminated

Algae in the aquarium is a recurring problem for all aquarists and we do everything to keep algae at bay … we even look for species of fish and mollusks, which basically feed on algae.

Sometimes the problem becomes so desperate that you want to take the aquarium apart and start from scratch.
Controlling these pesky algae in home aquariums is one of the main struggles that most hobbyists face.
Today there are multiple methods to remove algae.

As for algae attacks, the causes are quite obvious: there has been an imbalance in the aquarium.
But not all algae are eliminated in the same way, I will try to explain throughout this article, all the aspects that surround algae in the aquarium: why they arise, how to keep them within reasonable limits and how to eliminate them when their presence has become a problem.

Why do algae appear in the aquarium?

The main causes of algae blooms in the aquarium are excess light, or excess nutrients:

Inadequate aquarium lighting

If we maintain strong lighting in the aquarium (in some cases, lack of lighting), either directly (the aquarium is near a window) or indirectly (excessive lighting for hours or intensity), we are favoring the appearance of algae .
It can be somewhat incongruous, since direct or indirect light is necessary for life in the aquarium . In reality, lighting by itself does not generate the appearance of algae, what generates it is the «wrong» lighting for the biotope that we have in the aquarium : type and quantity of fish, in addition to the type and quantity of aquarium plants. The best option for lighting is to use  LED screens .

Nutrient imbalance or excess

The nutrients are given by nitrogen compounds and phosphates.
We provide these nutrients directly with the fertilizer of the plants, or indirectly, when feeding the fish.
The remains of the fish food, and the feces of the fish themselves, become great nutrients for the algae … when the proportion is excessive, and / or there are imbalances between them, we favor the appearance of algae.
If the aquarium water is in the right proportions, it is very unlikely that the aquarium will be attacked by an algae infestation.

Most common types of algae in the aquarium

There are many types of algae that can end up infecting the aquarium , but the most common are:

Diatom brown algae

  • Appearance: Brown algae belong to the diatom family , their color is brown, they have an oxidizing appearance and have a thin layer that covers a large part of the aquarium.
    They usually appear stuck to the bottom of the aquarium , between the substrate and the glass, where there is organic material in the process of decomposition.
  • Causes: The attacks of brown algae in the aquarium are usually mild and tend to disappear soon.
    They appear frequently when the aquarium is being cycled for the first time.
    It is usually due to decompensation of macros: due to excess phosphates or nitrates, due to poor lighting at the beginning of the aquarium cycling , among other factors.
  • Control: They are easy to eradicate from the aquarium, it is only necessary to eliminate them manually and increase the light level of the aquarium.

Green diatom algae

  • Appearance: They are easy to detect, so scandalous the appearance of the aquarium when they make an appearance.
    Unlike other algae, they do not necessarily settle on the glass or decoration, they basically colonize the aquarium water, creating a cloudy appearance.
  • Causes: The appearance of green diatoms is caused by an imbalance in the aquarium, a high presence of silicates and phosphates, which canbe caused byusing tap water and by the decomposition of frozen foods, such as mysis or brine shrimp .
  • Control: On the first day of treatment we will eliminate 50% of the aquarium water, we will siphon the aquarium substrate to eliminate as far as possible all the algae remains.
    We will add nitrifying liquid , to cause the nitrifying bacteria to destroy the excess nitrites.
    During the process, which can last from 4 to 5 days, we will turn off the aquarium lighting.
    To achieve a higher success rate, we will add an anti-algae.
    After five days we will repeat the water change, without adding anti-algae. From the seventh or eighth day, the algae will be in remission and we can start to turn on the aquarium lighting.

Green dot algae

  • Appearance: As the name suggests, they are algae that form green dots in different diameters.
    They can be presented on glass, decoration and plants.
    The algae that are on the glass are relatively easy to remove, but removing those that are on the plants is quite tedious and complicated.
  • Causes: Point algae appear when there is excess in the aquarium fertilizer, although it can also be due to an increase in nitrates present in the aquarium, and / or a decompensation with phostaphos, with alarmingly low levels.
  • Control: Its presence and proliferation can be reduced by changing at least 25% of the aquarium water every two days, until we are able to reduce the amount of nitrates. Monopotassium phosphate
    should be added at each water change.

Green dust algae

  • Appearance: They have a similar appearance to green dot algae: greenish dots of different sizes. Fortunately, they are rare and do not usually perch on the decoration or the plants, such as the green dot algae, we will see that their presence is concentrated on the aquarium glass.
    Another way to differentiate the green dust alga from the green dot is that when it is removed from the glass, we will see that a kind of «species» of very fine fabric appears, which detaches from the glass and remains floating in the water. This does not happen with the green dot.
  • Causes: Its appearance is usually preceded by an increase in phosphates and hardness of the aquarium water, especially an increase in calcium.
  • Control: Usually, by suspending the aquarium fertilizer after cleaning it well, making a 30% water change and keeping the parameters at the appropriate levels, the problem should disappear.

Filamentous green algae

  • Appearance: The filamentous green algae usually have two different aspects:
    * Some that are rather long, up to about 15 mm (1.5 centimeters) and not very dense. They appear on the leaves of the plants, the stems and the rest of the decoration of the aquarium. Its appearance usually coincides with small concentrations of ammonia.
    * Other filamentous green algae are small (no more than 2 mm) and dense. They usually affect the leaves of slower growing plants, on the crystals and on the aquarium decoration.
  • Causes: How it occurs with the appearance of most algae, its appearance is produced by an imbalance, which is usually due to a high presence of phosphates compared to nitrates, or a lack of nitrates.
  • Control: We will carry out frequent water changes to reduce the presence of phosphates. As the aquarium has a lack of nitrates, we will add potassium nitrate .
    The aquarium substrate should be siphoned at each water change.

Cyanobacteria blue alga

  • Appearance: Its name cyanobacteria, is because they are not algae, but photosynthetic bacteria that have a structure similar to that of algae.
    It has a bluish-green, viscous appearance, as well as a very characteristic ammonia odor and they are toxic to fish: they don’t come close.
  • Causes: It appears in the aquarium when there is an excess of phosphates, together with a deficiency of nitrates.
    They are common in planted aquariums, with many fast-growing plants, capable of depleting the nitrates present in the aquarium.
    Other causes are poor water circulation or the accumulation of decomposing organic matter on the substrate, causing situations of lack of oxygen.
    We can find it in the lower part of the aquarium, right between the substrate and the glass.
  • Control: At first they are easy to eliminate, with a siphon we can extract it easily, since they do not adhere … however, they are recurrent and reappear, also quickly.
    There is no conventional treatment that works well, you have to be very persistent, but to stop it we will make water changes of up to 50%, to increase oxygenation and eliminate phosphates.
    We will add potassium nitrate , to try to restore the balance.
    We will reduce the lighting of the aquarium, covering it for three days. During this period we will add 1 pill of Erythromycin 500 mg every day(one every 100 liters), together with potassium nitrate (1g, every 200 liters).
    Ideally, we should use anti-algae products, in addition to the typical: reduce the lighting, do not add CO2 , make the appropriate water changes and keep a close eye on the aquarium parameters.

Brown filamentous algae

  • Appearance: They are brown (obviously) and have filaments that can measure between 6 and 10 mm.
    They are unpleasant and slimy to the touch. They stick to almost all surfaces in the aquarium, especially plants and decorations.
  • Causes: They usually appear in aquariums that do not have adequate maintenance or are neglected at the beginning of the cycle. They appear because the levels of phosphates are very high , together with poor lighting due to lack or excess, as well as a lack of CO2 .
  • Control: To eliminate them, it is necessary to restore balance in the aquarium.
    At first we will change up to 50% of the water in the aquarium, we will suspend any type of fertilizer that we have in progress, as well as reduce the food we provide to the fish.
    We do not decrease the lighting, as when we try to combat other types of algae, we will increase the CO2 to the maximum that the aquarium supports, at least 25 ppm.

Short red algae rhodophytas

  • Appearance: They are algae that have very short hairs, of a dark green color, sometimes almost black, and appear on old leaves and slow-growing plants.
  • Causes: These algae can be seen in aquariums with excess phosphates or ca
    cium (
    kH higher than 6 ) and a shortage or lack of CO2.
  • Control: The optimal way to keep them under control or eliminate them is to return to the balance of nutrients. We will start by making water changes, which will help us find the balance.
    Usually when the parameters are rebalanced, the algae disappears. However, the situation may arise that we have some plant leaves that we are not able to eliminate, in this case it is best to cut them and eliminate the problem.

Brush algae

  • Appearance: They are called brush algae because they grow in compact groups of tufts ranging from 6 millimeters to 12 millimeters; They are dark green in color, sometimes almost black, and grow on old leaves, logs and decorative rocks.
  • Causes: They appear in aquariums with excess iron and phosphates, as well as a shortage or lack of CO2.
  • Control: We will eliminate all that we can by siphoning the aquarium.
    The excess of iron, causes that the phosphate cannot be absorbed by the plants.
    Water changes are not very effective in eliminating them, so the best way to eliminate it is by adding 10 ml of hydrogen peroxide for every 100 liters of water and 5 ml of glutaraldehyde for every 100 liters.
    The hydrogen peroxide will be applied in the morning and the Glutaraldehyde at night. We will carry out this treatment until the algae are completely eliminated, which can be about 10 days.

Everything you need to maintain your aquarium

  • Best digital pH meter
  • Best Aquarium Test
  • Best anti-algae
  • Best bacteria for aquarium
  • Best siphoner for aquarium
  • Best Aquarium Water Clarifiers
  • Best reverse osmosis filters for aquarium
  • Best UV lamps for aquariums

Avoid the appearance of algae in the aquarium

The appearance of algae in the aquarium is very frequent, and in most cases it is not a problem.
There are many fish that feed on algae , and it is only when there is a strong imbalance that the algae become a pest and it is necessary to act decisively.
Many fish and some invertebrates (snails) are usually introduced into the aquarium to try to fight and keep algae at bay, preventing their growth from being a problem.
When algae already become a problem, then we have to take action.
Sometimes with a simple treatment we eliminate the problem, although it is always good to use an anti algae product, to achieve its total eradication.

Anti algae fish

  • Crossocheilus siamensis or Siamese Flying Fox : This fish is a good eater of filamentous or brush algae, however they are very difficult to find. There are several fish in this family, such as the flying foxfish, which has a brown color with a very marked black stripe, a fine one and a golden one. Both fish are not aggressive and are good company for discus and small tetras.

Flying Fox Fish

  • Black Mollies : They are the perfect candidates for removing algae in the adaptation period of a planted tank. It is a species that eats all kinds of algae during the adaptation period.
  • Otocinclus : They are very good algae eaters, although some seem to prefer the slimy layer of fish to algae.
  • Plecostomus : This name refers to a wide variety of fish with a sucker-shaped mouth. The smaller types of Plecostomus, such as the bristle-nose plecostomus or the Pekoltia, are the most indicated to combat algae, since the larger ones tend to eat the plants together with the algae.
  • Farlowellas: Farlowellas are excellent for eradicating algae in aquariums, although they are very sensitive to water conditions.

Invertebrates anti algae


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