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How to get rid of algae from my tropical aquarium?

auqarium photo from the surface

Algae is a common problem in a tropical aquariums. Even though aquatic algae is not esthetically desired, it does not pose any harm to neither the tropical fish nor the plants in your fish tank.  However, the presence of algae will make the task of cleaning the tank more tedious, especially the ornaments and the  artificial plants.


The above algae infestation has developed over a 2 weeks period, due to the aquarium being exposed to direct sunlight from the window visible on the back of the photo, our technicians carried a full aquarium cleaning session and recommended moving the tank to a different location. The result was clearly visible on the following photo.


Algae can be in various forms and can have different colours, to name a few :

  • Green algae in long or short filaments called Oedogonium
  • Green moss like Algae  growing  on surfaces called Cladophora.
  • Brown Algae called diatoms.
  • Blue-green algae called Cyanobacteria.
  • Fuzzy algae.
  • Etc.

Throughout the years  we have encountered this situation countless times. From our own experience and according to what is commonly known about tropical aquariums there are few main factors that promote Algae proliferation:

  •  Fish tank Exposure to sunlight: Whether the exposure is direct or indirect through reflection on surfaces ( glass, glossy tiles, stainless steel surfaces etc.). Sunlight is needed for algae to grow through photosynthesis.
  • Exposure to Excessive artificial  light: Leaving your aquarium’s lights on, continuously ,  for more than 12 hours a day may lead to algae growth.
  • Poor lighting conditions: Sometime the other way may lead to brown algae growth. If the tropical aquarium does not receive enough light for a prolonged period especially artificial lighting, brown like substance will show in the water, those are Diatom algae spores.


  • High level of phosphate in the aquarium’s water : Phosphate acts as a fertiliser for algae and all derivatives  of Cyanophyta (plants etc.) which extract its energy from light through photosynthesis in order to grow.  The main sources of phosphate in an aquarium come from the water itself (if it is hard water rich in minerals versus Soft water which is less rich in minerals) or/and from excessive amounts of nutriments and fish waste. If you live in the Greater London Area the Thames Water had made available a tool to check the level of water hardness in your area.

If your tropical aquarium is subject to the conditions mentioned above  ( Lighting conditions and hardness of water), algae will proliferate.
Some cases of algae infestations are mild others are more severe. You have to bear in mind that algae is as natural as anything else in your fishtank and you should not be alarmed if few spots of algae appear occasionally. However, you will have to make sure that:

  • The lights in your tank are set properly.
  • The aquarium is not exposed to sunlight neither directly nor indirectly.
  • The level of Phosphate and nitrate is low. Be aware that this is effective only in aquariums with  no live plant. Aquatic tropical live plants will need phosphate and other minerals to grow and having very low levels of phosphates will starve them.

It is ideal to have all of the conditions right however sometimes you will find yourself constrained with conditions beyond your control. If you live in a very bright place where you can not place your tank out of reach of sunlight or if the water supplied in your area is hard water, you might want to resort to eliminate at least one of the factors contributing to the unusual algae growth.

If you are experiencing a severe algae infestation, these are the steps to follow that might help with the situation:

  • Remove your aquarium from direct or indirect  sunlight. If you can not do that, consider  fitting blinds on the aquarium and apply them during the times of day when the sun light is reaching to  the tank.
  • Clean the algae off the whole aquarium and its content.
  • Treat the aquarium chemically with an anti-algae solution: For that matter you will have to remove the carbon and ceramic Medias in the aquarium filter in order to allow the solution to eradicate the algae at a microscopic level. Leaving the Medias while applying the solution will simply filter the solution away
  • Perform 50% water change .
  • Reduce the duration of time in which the aquarium lights are switched on if necessary.
  • After few days and  up to two weeks of adding the anti-algae solution, you should reinstate the carbon and ceramic media in the water filter in order to clean the phosphate neutralising solution away.
  • Once you  are convinced that the water had stabilised and that the most of the algae treatment chemicals have been filtered away, you may want  to   introduce specific fish and invertebrates ( such as shrimps & snails) which feed on algae. These organisms will only do a very small portion of the task of getting rid of the algae. The radical solution would be have optimum lighting for your aquarium and prevent exposure to sunlight.
  • Finally, you carry on with regular aquarium maintenance and water change.

Performing the above steps will reset your aquarium’s ecosystem chemically. This process is rather not recommended for its invasive nature to the  fish in the long run.  However, if algae growth is getting out of control, you may be compelled to perform it . Moreover, if your aquarium holds live plants this will affect them in a way that there will be less phosphate in water for them to absorb.

To summerise, when faced with an algae infestation problem you have to proceed by elimination and try to isolate the cause of the excessive algae growth. Treating the symptoms will not provide a long term solution to the problem .  However, we can confidently state that if your tropical  fish tank is suffering from algae , the cause of it will be primarily either:

  • Bad management of the lighting system of the aquarium ( too much light or not enough of it);


  • Exposure to sunlight.