Algae in the aquarium - descriptions, removal methods

1. How can algae get into the aquarium?

Many aquarists think that a well-maintained tank should not have any algae. But the truth is that a small amount of algae will always be present in even the best-kept aquarium. A small amount of algae tell us that we have adequate amounts of nutrients and good amount of light. Excess algae occurs when the balance is not kept and there is too many micro elements in the water to a number of plants. Especially phosphorus is responsible for the plague of algae. When there is a lot of nutrients available than it is good situation for algae which will use those minerals to grow rapidly. If the nutrients balance is kept then algae lose the fight for nutrients with plants. The truth is the algae is a permanent residents in the aquariums and it depends on us if we let them to develop or try to prevent their plague.

2 Nutrients for plants and algae

Plants like other organisms need food. The most important nutrients for plants are:

  • Nitrogen compounds nitrates and ammonia are harmful for fish. Nitrifying bacteria converts nitrates to safe elements. Nitrates exist in fish droppings, rotting parts of plants and in not consumed food which stays in the substrate.
  • Carbon dioxide is produced by the fish in the process of respiration. It also is produced in the process of organic compounds decomposition such as manure, rotting leaves of plants and uneaten food. You can also fertilize the plants by supplying the carbon dioxide from the cylinders containing compressed carbon dioxide. Importance and control of carbon dioxide.
  • Light, without which it would not be possible to carry out the process of photosynthesis. You should try to avoid sunlight and use only artificial lighting so that you have full control over it. Sunlight increases the algae growth as well as too strong artificial light or too long period that light is on also will increase the algae growth. More about light and its role in the aquarium you can find here.
  • Micro and macro elements which include magnesium, potassium and iron.
  • Phosphates - minerals containing phosphorus compounds largely contribute to the growth of algae. The excess of these compounds leads to the plague, which is hard to handle. You should closely monitor the amount of phosphorus in the water and quickly respond to the increase of more than 0.5 mg / litre. Read more information on how to regulate the amount of phosphate in the aquarium

3. Fish that eat algae - algae slayers :)

Excess amount of algae can be controlled by keeping fish which main food component is algae. The most popular are:

Note: generally it seems that Sucking Loach eats algae but this is true only for young individuals. Older individuals can even eat softer plants.

4 Types of algae

4.1. Blue-green algae also known as Cyanobacteria or Blue-green bacteria

They are actually cyanobacteria and not algae like everyone thinks. Those bacteria are the evidence of poor water quality (excess phosphates and low level of nitrates). They spread rapidly covering everything in the aquarium. They can cover the plant in such a way that it may kill it. They have a greenish-blue color and produce toxins harmful to fish. In the aquarium the consistence of the Blue-green algae is something like jelly which can be found on plants, substrate, rocks, etc. At night it can reduce the amount of oxygen by using a lot of it. You can remove them from plants by rubbing the leaves with your fingers. This blue-green algae have an unpleasant odor. It can be found mostly in reservoirs with low contents of nitrogen, high content of the phosphorus and poor water circulation. If your aquarium is attacked by this algae you should try to remove as much cyanobacteria as possible from the tank (the more than better). It is also required to stop feeding the fish for a while to reduce amount of phosphorus in the water. Please make sure to replace about 50% of the water in the tank and keep the amount of nitrate at about 20mg/L. You can also use external filter with material with small holes for example perlon wool. Perlon wool is a fabric that gives better filtering and helps to remove even the smallest micro-contaminants from the water. It should stop growth of the blue-green algae but you should clean the filter every two days.

4.2. Diatoms

algae, diatoms larger

This algae are evidence of light deficiency and excess of phosphates and nitrates. When starting an aquarium this algae may occur in strongly lit areas although this algae prefer dim lighting. They have a brown color and grow on the glass, plants (blocking their access to the light) and decorative elements. If you try to get rid of them never use chemicals. Diatoms produce spores and then come back after chemicals will stop working with a vengeance. You can get rid of them by turning the light in the aquarium for longer. Remember to use common sense when doing it to not overdo it because instead of diatom you will get other algae instead. You also need to reduce the amount of nutrients by partial water exchanges.

diatom algae

Diatoms are eagerly eaten by Golden Oto. You can let a few Golden Otos in the aquarium to help in the fight. Removing of the diatoms from the aquarium should be started from removing as much as possible using mechanical methods such as scraping the glass with your fingers or by rubbing the leaves of plants. Also water exchanges and taking care for the water parameters should stop their invasion.

4.3. Red algae or Rhodophyta.

Their color is a combination of blue phycocyanin, red phycoerythrin and the green chlorophyll. They can be reddish, bluish green algae, etc. To the aquarium they get with water or plants. The type which looks like brushes likes flowing water and often begin their attack by settlement at the outlet of the filter. It is very difficult to get rid of them. They attack the leaves and if their concentration is too high results can be drastic. They may lead to the death of leaves and than to death of the plant. Heavily infested leaves should be removed. To fight Red Algae you need to send Siamese Algae Eater and Mollies. Group of those fish should reduce amount of red algae. You must know that if you have moss in the aquarium it may be eaten too. If we have a tank with CO2 system to feed plants than frequent water exchanges combined with desludging (which should reduce the amount of phosphates) and taking care of water parameters and a slight increase of CO2 to about 30mg/litr (which should slightly lower the water pH) - should reduce their development or even force algae to retreat. You should also check if you have sufficient nitrates. Their lack will stop plants from consuming phosphorus from water. This phosphorus will became available for the algae and will increase their growth.

If we do not have CO2(carbon dioxide) system than we should stop water changes during treatment and overdose the carbon in the form of liquid preparations: Flourish Excel or EasyCarbon. Fish should be fed using smaller portions of food so the entire portion is eaten immediately and nothing falls to the bottom. The tank must not be to crowdy because it will continue to provide excess amount of nutrients which will increase algae growth (fish waste = phosphorus). If algae attacked substrate you can take part of it, boil it and pour back into the aquarium. Algae do not like acidic water (pH below 6.9).

To win with this algae use all the methods at the same time. Failure to do use all described methods will let algae to start wining. There is some photos sent by our reader Patrick. I hope you win the fight against the intruders. It is also worth to read the 5. Prevention and removal of algae where you can find additional methods and techniques which will help you to fight against algae. We described there a method with tea as very effective way to remove algae.

4.4. Chlorophyta a division of Green Algae.

This algae causes algal bloom in water, which occurs mainly in tanks with direct sunlight or very strong artificial light. Water algal bloom can cause fish gills sticking and reduce the oxygen content in the water. They can be removed by filtering water using filters with small holes. You can also use an external filter with UV lamp that kills algae floating loosely.

More pictures can be found by visiting the link Gallery of the green algae.

5. Prevention and removal of algae

To prevent algae invasion you need to keep appropriate micro elements level in the water and high water quality. You have to be careful with amount of phosphorus which help algae to grow. Firstible you should not use any plant fertilizers which contain phosphorus. Small amount of phosphorus reduces plant and algae growth. There is a race for phosphorus between plants and algae. Usually plants win this race but if there is to much phosphorus in the water than plants can not use it all and algae is able to grow using surplus of phosphorus. It is good to keep slight surplus of nitrates, potassium and carbon dioxide in relation to phosphorus and also to maintain lighting at the level of 0.5-0.7 [W / L] . Humus compounds can be very helpful in algae removal (humus is slightly lowering water pH to level of 6,5-6,9). There is quite a lot of humus compounds in the lignite (hardened brown coal) which can be placed on the bottom of the aquarium as a decorative element. Additional fertilization CO2 also acidified water. With the carbon dioxide do not go to far because the pH may drop too much and you will kill all the fish. A safe level is up to 30mg/L.

cone of black alder

Another form of the humus compounds is a cone of black alder. You can use dried black alder cones to prepare a brew (pour boiling water and keep it covered until it cools down) or as a layer in the internal or external filter. It's hard to determine the right amount so you should carefully keep an eye on the pH level. Average 8-13 cones are used for 100L of water in the aquarium.

Another interesting way to lower the pH is a tea or green tea. You can make a tea brew, cool it down to around 22-25oC and immers plants attacked by the algae in it. You can also add brewed tea to the aquarium in the right proportions. Tea contains tannin, tannins and humus which help in the fight against algae. To brew the tea use 1 tablespoon of the tea and boil it in 250ml of water. This amout of brew (after cooling it down) is enough for 100 litres of water in the aquarium. As you can see algae do not like low pH but you should also watch amount of phosphates which help algae to grow and keep the level of the phosphates below 0.5 mg/litre.

It is easier to prevent algae than to remove. When buying new plants to your aquarium you should remove the algae and quarantine the plant. It should protect you from getting new type of algae to your aquarium.

There are also methods which use UV light or special chemicals for algae (chemicals are not recommended). If you have aquarium with fish only (no plants) then you can use an appropriate UV sterilizer that will remove all algae. But when we have plants than do not use this type of solution for a whole tank. Instead you can use special filters with UV lamps. Water flowing into the filter is exposed to UV destroying algae cell nucleus (but it also destroys mineral elements). This method works with algal bloom, but does not help with the algae growing on the plants in the aquarium. Also this is only removing effects and not the cause of the algae pollution. There is no need to use chemicals to remove algae as there are natural ways you can use to get rid of algae.