Don’t give algae a chance!

Algae doesn’t always spell disaster!

In biological terms, algae are just normal plants. Algae spores, which are algae germ cells, naturally appear in water on decorative items or new plants and initially are not too serious. In fact, a light covering of green algae is actually a sign of good water quality. It is also entirely normal for a covering of algae to appear in the first few weeks after setting up a new aquarium. This tends to disappear of its own accord after a relatively short period of time. However, if algae suddenly develops in a well-established aquarium and manages to grow over the other plants, this jeopardises the water quality and the healthy, biological balance of the habitat. Sudden, intense algae proliferation is often a clear sign that the biological balance in the aquarium has already been heavily polluted by over-feeding or other organic waste (unnoticed dead fish or snails) and is subsequently in trouble. Action must be taken to resolve this to avoid ending up with an unattractive aquarium or even losing fish. However, a gradual increase in algae growth also suggests that the water contains a surplus of phosphate and nitrate. This normally means that the tank is overstocked in relation to its size. Algae is also more likely to form in aquariums without plants.

Prevention is key

It is generally accepted that prevention is always better than cure and this also applies when dealing with algae. In fact, aquarists can start preventing the spread of algae as soon as they set up a new tank. This begins with the substrate, which should have the right grain size (usually 3 to 6 mm gravel). Provided that the depth of the substrate is sufficient, suitable, fast-growing aquatic plants bought from specialist retailers will receive enough support to develop properly and make it difficult for algae to grow by competing for nutrition. In addition to this, the substrate should also be mixed with Tetra CompleteSubstrate or Tetra InitialSticks , as well as Tetra NitrateMinus Pearls, when setting up a new aquarium. The first two products mentioned are slow-release fertilisers and promote healthy plant growth without polluting the water, whilst the Tetra NitrateMinus Pearls reduce the level of the unfavourable algae nutrient nitrate. They work their way into the substrate and reduce the nitrate content over an extended period of time (up to twelve months) to ensure better water quality for the long-term.

In addition to the pearl granules (Pearls), the purely biological substance is also available as the liquid Tetra NitrateMinus to allow for easy reapplication at a later date.

Conducting a weekly test of the main water values will give you an indication as to whether the aquarium is in a stable and healthy condition. The Tetra Test 6in1 test strips make it easy for you to reliably test the six main water parameters, including the nitrite and nitrate content. Both values should be kept at a very low level. You can help to prevent an unfavourable increase in these values by carrying out water changes both promptly and regularly. Alternatively, by using the care product Tetra EasyBalance, you can also safely reduce the levels of phosphate and nitrate, which promote algae growth, without carrying out traditional water changes. This prevents unwanted algae growth, particularly when the tap water already has a naturally high nitrate content.

Causes and remedies:

The following table provides information on which steps should be taken and which parameters should be tested to prevent the formation of algae:


  • Light
Possible causeSolution

The sun is shining into the aquarium

The sun is shining into the aquarium

Short or long lighting time

Around 12 hours is an appropriate time

Incorrect lighting

0.5 watts per litre of water are suitable

Old lighting system

Replace lamps after no later than a year
  • Care
Possible causeSolution

Too long between water changes
Use Tetra AquaSafe every 14 days as a minimum or use Tetra EasyBalance once per week

Leftover food
This should be removed. Tetra NitrateMinus combined with Tetra EasyBalance can be used to tackle a high nitrate content and also extracts phosphate

The rule of thumb is to keep to 1-2 litres of water per cm of fish

Infrequent filter cleaning
This should be carried out every four weeks by adding Tetra Bactozym und Tetra SafeStart
  • Plants
Possible causeSolution

Few aquatic plants
Add new, fast-growing plants that will extract nitrogen compounds from the water
Aquatic plants are not fertilisedCombine Tetra PlantaMin with Tetra Crypto Fertiliser
The water’s surface is covered with plantsThin out and trim the plants

What are the different types of algae?


  • Green algae
Possible causeSolution

– Excessively polluted water with a lack of competition for nutrients

– Use Tetra products to enhance plant growth
– Perform regular partial water changes
– Use Tetra EasyBalance
– Tackle algae using Tetra products
  • Blue-green or smear algae

Possible cause


– Compacted or poorly fertilised substrate
– Poor water quality
– High levels of pollution

– Improve the condition of the substrate
– Remove mulm build-up from the bottom more regularly
– Perform regular partial water changes
– Use Tetra EasyBalance to enhance the water quality
– Tackle algae using Tetra products
  • Diatoms

Possible cause


– Excessively polluted water
– Insufficient or poor lighting

 Use Tetra products
– Perform regular partial water changes
– Improve the lighting – provide 10-12 hours of lighting per day
– Tackle algae using Tetra products
  • Brush or beard algae (particularly stubborn algae)

Possible cause


– Water is excessively polluted with nutrients
– Lack of CO2
– A potentially excessive degree of water hardness

– Use Tetra plant fertilisers
– Use Tetra CO2 Optimat
– Tackle algae using Tetra products
– Perform regular partial water changes
– Reduce the hardness and pH value and use Tetra EasyBalance to stabilise the levels.

Should these measures not succeed in tackling the algae, you can use the various Tetra anti-algae products to eliminate the unpleasant greenery quickly, directly and efficiently. It is always advisable to manually remove as much of the algae as possible beforehand, particularly when dealing with blue-green or smear algae.

Tetra AlguMin*

Mild biological treatment for combating algae.

  • for use at the onset of algae problems
  • broad-spectrum action to combat all frequently occurring types of algae
  • contains humic substances as a natural anti-algae agent
  • when used correctly, it is harmless to fish, plants and micro-organisms

Tetra Algetten*

For the prevention and long-term elimination of algae.

  • depot principle: the concentration of the active anti-algae agents increases slowly in the aquarium water – leading to a mild, long-term effect with dispenser for long-term application

Tetra Algizit*

Solves even persistent algae problems.

  • contains intensive agents to persistent prolific algae growth
  • „emergency stop„ for persistent algae growth
  • the water is not discoloured

Tetra AlgoStop depot*

Solid tablets for targeted long-term control of algae in freshwater aquariums.

  • destroys brush and thread algae
  • prevents the growth of algae
  • contains highly effective algicide with broad-spectrum action
  • with depot agent for the gradual release of the agents over a period of approximately six weeks
  • no damage to aquatic plants, fish or micro-organisms when used correctly

* Use biocides safely. Always read the label and product information before use.