We will identify each type of freshwater algae and then learn how to eliminate them. However, you should know that on a newly installed tank it is normal to have algae, do not worry, everything will return to order without your intervention.
On the other hand, in a normally broken-in tank, the proliferation of algae always comes from a deficiency, from unsuitable lighting or from the parameters and quality of your water. An explosion of algae is a sign of a significant imbalance.

Algae benefit from an excess of nitrates (No3) or phosphates (PHo4) or from the lack of a trace element that paralyzes the growth of plants. A poorly maintained filter accelerates the growth of algae by leaving nutrients in the water that benefit them. Filters produce nitrates and too much nitrates grow algae! it is therefore necessary to wash and maintain its filters carefully.
There are 2 main groups of algae: Macro-algae which are fixed in a thallus (organized like a plant) and phytoplankton, which floats in open water (clouds the water).

To limit or avoid the invasion of algae when starting a new aquarium

You are advised to:
- plant as many fast-growing plants as possible (see list in section "plants for our loulous") to create competition, (even if it means removing some within 6 months when the balance begins to improve and replace them small little by little by other plants which grow less quickly but which will be larger or more decorative; Anubias, Echinodorus)

- do not light all the neon or led tubes at once for 12 hours ....
but only connect 2/3 of the lighting for about 10 hours then gradually increase over 2-3 months.
To limit the presence of algae, you must
- good lighting, 1 Watt for 2 liters of water. In lumens: ideally 30 lumens per liter) for 11 to 12 hours and in one go. (No cut, the plants do not really appreciate. For our axolotls we can clearly reduce this number of lumens of course but you have to choose the suitable plants (see plants section) which will be fast-growing plants, which allows them to compete with algae;
- LEDs with a temperature (see lighting section) of 6000 to 7000 K or neon tubes changed every 10 to 12 months. After this time, they still light, but their spectrum has changed and it is the algae that benefit.
- levels of Nitrates and Phosphates kept low: The major effect of nitrates is to boost the growth of algae, since these are their basic nutrients.
- a well-monitored iron level. Too much iron encourages algae and not plants.
In general, an iron level of 0.05 to 0.1 mg / l is recommended.

Bad advice
Avoid using anti-algae products, which upset the balance of the aquarium and create other problems. Anti-algae also act on plants by growth inhibitors, they do not only block the growth of algae ... but they also stop the growth of plants which again promotes the growth of algae and therefore the remedy is worse than evil!
It is sometimes recommended to cut the lighting for 4-5 hours in the middle of the day! This affects the algae, but especially the higher plants that are the plants.

We manage to limit algae by respecting basic rules
- regular water changes 30% per month. Overpopulation = pollution.
- lots of plants, and give preference to fast growing plants.
- no overfeeding.
- regular monitoring of nitrates and phosphates.
It is useless and harmful to aim for a rate of zero No3 nor zero Po4, a little Nitrates and Phosphates are necessary.
Ideally, a rate of 15-20 mg / L of NO3 and a rate of 1 mg / L of Po4 prevents algae growth and promotes plant growth!
In the event of a lack of No3, it is recommended to space out the water changes or even to slightly pollute the tank, for example by increasing the distribution of food to increase the nitrogen load a little. We can also simply add Nitrate of potassium, (KNO3). Clean the new plants well to avoid incorporating algae in your aquarium, adding a few drops of bleach but never more than a minute in this mixture.


Siliceous or diatom algae

They are present on rocks, elements of the decor or even on the sand. It is most often algae present on a very young tank as we have seen above. On an older tank this means that the lighting is no longer sufficient or that the water no longer contains the necessary nutrients. In a new tank, brown algae (diatoms) are almost inevitable but they are not very invasive. They usually disappear on their own in 1 or 2 months as soon as the aquarium balance improves. There is not yet a balance between the quantity of plants, the number of fish and the doses of food distributed in the tank. The bacterial population of the aquarium is developing, the plantation must grow, in short the aquarium needs time for a more or less precarious balance to be put in place. Normally, if the water and lighting settings are right, the brown algae will slip away over time. Depending on the region, the mains water may have a high silicate content (there may be up to 30 or 40 mg / l of silicon dioxide (SiO2)) in such a case, the use of water reverse osmosis may prove to be essential.

Encrusting, lining seaweed

They arrive very quickly in a new tank, and are generally a sign that the balance is good. They are relatively discreet, grow on the decor and windows, but do not invade everything. Snails (especially Neritinas) and most herbivorous fish eat them. On the glass of an aquarium intended for axolotls they are simply removed by using an old credit card or a loyalty card as a "scraper". It does not scratch the windows and it is very effective.

Filamentous green algae

They grow in healthy bins, good news, right? They have the same requirements as plants, their appearance is a good sign, they are ugly, but not harmful, it is enough to remove them by hand or by wrapping them around a stick (cotton candy), because they enter into compete with plants and consume the same nutrients. Oedogonium They appear in the form of filaments of 2 to 20 mm, firmly attached to the leaves or to the decoration. These "hairs" are very fine and light green and quickly cover the upper surface of plants like a fur ... Not to be confused with brush algae. They settle on tall leaves, close to the light and all plants can be dressed like this. These algae reproduce very quickly and can invade a tank that has too high a nitrate level. Natural method: To eradicate them, it is generally sufficient to find the right water parameters by lowering the phosphates and especially the nitrates by large regular water changes. Ampullaria, planorbs and some fish graze them. Phospahates and nitrates can also be reduced by using resins or special filtering masses of the genus Nitrat-ex or Phos-ex. 9 times out of 10, it suffices to restore the correct parameters to eliminate the algae. There is no point in treating with an anti-algae product if the cause of their proliferation cannot be found, they will return systematically and the plants will be increasingly weakened. Many algaecides contain copper, which is very harmful to the invertebrates in the tank and which will therefore kill snails and shrimps, which are valuable auxiliaries in the fight against green algae. Fish without scales, such as Loricariids, do not like copper build-up either. And obviously the axolotl which would die very quickly.

Cyanobacteria (slimy blue / green algae)

Fish or snails do not eat them because they are toxic and commercial anti-algae products have no effect. It occurs more easily in tanks where the nitrate level is almost zero or even not measurable. It is therefore sometimes necessary to add potassium nitrate (KNO3) But before playing the apprentice chemist come and seek advice, a too rapid increase would have devastating effects. Never more than 5ppm in the end. And it is especially necessary to have confirmation on the identification of the algae.

How to get rid of it in a natural way?
It is necessary to remove the greatest possible quantity by siphoning them every day, by cleaning very carefully the parts of the decoration which are affected (wash them in 70% bleach and 30% water then rinse well and dry), changing more water and more often, in short by significantly improving the quality of
the water in the tank. But that's not all...

Cyano has been present on land (and in rivers, lakes and sea) for 3.5 billion years. It is adapted to survive!

It uses the carbon present in the air and in the water, so in the event of cyano leaving, it is imperative to cut the co2, if you inject it.

In addition to this, you will need to know more about it.

The water changes will not work miracles, in fact the cyanobacteria uses carbon from the air and nitrates are not the only ones responsible for its spread elsewhere.

Anti algae products are ineffective !!

In addition to this, you will need to know more about it.

The causes :

water saturated with nitrates, phosphates and silicates and other organic matter whose threshold has exceeded the reasonable, the tests do not detect them and this water provides permanent nourishment for cyano.

the water does not have a "dirty" appearance for this it can even be crystalline)

In addition to this, you will need to know more about it.

Often the multiple attempts to remove this "algae" only through water changes and a blackout are in vain, we see their return after three days

The water purifier, resi-filter clean water from zolux works well and one day after more traces of cyano normally.

Lighting is not the cause of everything but indeed like low oxygen water (so think of oxygenating plants) and a stagnant environment, all these elements greatly favor its appearance!

Summary: aqua well planted, water well stirred and oxygenated and you will be able to avoid its appearance.

These are red algae that can appear in a black color, also green. They grow in thick clumps on slow growing plants like anubias, certain ferns or echinodorus and even on your soil. They appreciate the current, they are often seen in well-stirred areas of the aquarium and on the filter outlet pipe. They often come from a lack of phosphates. Or an imbalance between phosphates and nitrates (the main cause of many algae) A ratio of 10 nitrates to 1 phosphate is ideal (10 mg / l of nitrates for 1 mg / l of phosphates). All these algae benefit "thanks" to poor maintenance: infrequent or irregular water changes, ditto for your filter media. Personally I had to fight against these algae brought by new plants which were affected, it was enough to place them with water from their aquarium in a bucket in the dark for 15 days and the plants still affected remained one at a time. two more weeks until eradication of this algae.

Brush algae

Green algae

are, for their part, linked to too intense light. They cover the decor, the sand, the windows and the plants. To eliminate them, it is enough to reduce the lighting or change the power of the neon lights. They are also often present when the aquarium is exposed to outside light, to the sun. In this case, only moving the bin can remedy the problem or obscure the windows.

Brown algae ,

conversely, are linked to a lack of light. They are often present when filling the aquarium with water, and disappear by themselves within a few weeks. They spread over plants and decor like fine rust dust. By rubbing gently with your finger, they disappear.

Other algae, such as blue algae, brown filamentous algae, brush algae are mainly due to poor balance in the aquarium. It is therefore not uncommon to meet them in a newly filled or poorly maintained tank.

Too high levels of nitrates and phosphates benefit the algae, which then spreads quickly. Check the aquarium water settings.

Some tips to fight against algae:

Monitor the good health of your plants, they are in direct competition with algae.

Do regular aquarium maintenance by changing 20% of the water every week, taking care to siphon the bottom with the hose. Temporarily reduce the lighting duration

Check the condition of the neon tubes. After a year, they must be changed.

T est the quality of the aquarium water : a high nitrate level is often responsible for the appearance of algae. Also test for phosphates. It is necessary to have a proportion of 10 to 1 between nitrates and phosphates: with a rate of nitrates at 10, there must be a rate of phosphates at 1. An imbalance between phosphates and nitrates benefits the algae.

Decrease the amount of food and increase water changes if the nitrate level is too high.

Eliminate all the leaves of plants affected by algae , this will prevent their spread.

If your population allows it, prefer rather acidic water, a basic pH would promote the proliferation of algae.

In a planted aquarium, add fast growing plants , they absorb nitrates and prevent algae from spreading. The more plants there are, the less algae there is! Avoid adding too much liquid fertilizer to your plants: an excess promotes algae.

Of course, also be careful not to overpopulate your aquarium , the resulting pollution promotes algae.

In any case, never use chemicals to overcome it. They are harmful to the balance of the aquarium and are not very effective. In addition, very often, if there has been a result, the algae will return afterwards since the cause of the problem has not been eliminated.

Instead of attempting chemicals, in extreme cases you can attempt to submerge the aquarium in complete darkness for 5 days. This technique seems to work, although again it will not solve the cause of the problem.

Either way, be patient, algae in a newer aquarium is normal. After a maximum of 6 months everything must be back to normal.

Click the picture to order it


Chihiros Doctor Twinstar algae inhibitor - Electronic system against the development of algae in the aquarium - Third generation - With converter adapter

  • Dimensions of the filter: 62 x 62 mm - Dimensions of the filter net: 95 x 50 mm.

  • Material: plastic.

  • This inhibitor suppresses the growth of algae while protecting fish and axolotls of course. It covers up to 90% of the size of aquariums on the market and reduces user costs.

  • Inhibits algae and promotes plant growth. Slows down the initial growth and reproduction of phytoplankton.

  • Activates trace elements to stimulate plant growth. Eliminates pathogens including those which are carcinogenic.

In addition to this, you will need to know more about it.