Salt Water Articles

Controlling the Growth of Algae in the Aquarium Part 3

We came to the last step of the methods to control the growth of algae in aquarium: the biological control.

Biological Filtering

Biological filtration is the method universally used for filtration and purification of aquarium water. Bacteria located in the sand, in live rocks and on other porous substrates such as Heterotrophic Bacters which are responsible of converting the Amino Acids into Ammonia (NH4), the Aerobic Nitrifying Bacteria transform Ammonia in Nitrites (NO2) and Nitrates (NO3) and the Anaerobic Bacteria Also also called Denitrificants decompose nitrates and release nitrogen in the form of gas (found in deep sand layers in tanks with DSB or Deep Sand Bed).

Algae Filtering

Photo by Simone Grimaldi

Controlling the growth of algae using algae is a paradox, but with this type of filtration you really can avoid the plague of algae in the aquarium. The algae are grown on grids that are connected to the filter system circuit.

This system is commonly used overseas and takes the name of ATS or Algae Turf Scrubber which simply means algae filter. ATS consists of forcing the water to pass through a plastic grid like in the photo, enlighten by a special light that stimulates algal growth, so the presence of algae is limited only to that portion and therefore they do not invade the main tank.

(To learn more you can read this article: ATS )


Filtration using Macro Algae 

Photo by Felice Panico

Filtering by means of Macroalgae is another system tested by the hobbyists which helps to counter the growth of algae in the aquarium.

How does it work?

Macroalgae such as Caulerpa, Chaetomorpha, Graciliaria, etc., are used inside Refugium where, without falling prey, they grow luxuriant and absorb pollutants such as NO2, NO3 and PO4. Even algae for growing need Nitrite, Nitrate and Phosphate therefore the presence of a refugium with Macroalga, illuminated with inverse photoperiod, limits the growth of the troublesome algae in the tank.

The Refugium is an optional tank to be added to the system, with different management methods such as DSB (Deep Sand Bed), Miracle Mud by Leng Sy or without a sandy substrate. The Refugium, in addition to having the advantage of controlling the growth of algae by helping water purification, also offers a safe space for many microorganisms that could not be so easily reproduced and survive  in the main tank as they would fall prey to corals, invertebrates and fish .





As the use of algae filters has become popular, the same is happening with the Red Mangrovie (Rhizophora spp.). This plant has negligible benefits in the aquarium, but we think it has many more disadvantages as regards insertion in aquariums. One of the many is the presence of a large radical structure that causes significant changes in DSB tanks. The other disadvantage is the removal of a large amount of nutrition (trace elements, etc) from both the substrate and the water. The last disadvantage is the remarkable evaporation of the water caused by the plant having the roots in contact with the water and the leaves lit by a hot light source such as the HQI.


Sea Grass

Carpet of Posidonia Photo by Sergio Poppi

With this name are shown the marine phanerogamae that produce large carpets similar to meadows (Posidonia, Thalassia, Zostera, Cymodocea, etc.). Seagrass like mangroves, does not grow with the speed of algae and therefore is not effective in controlling the polluting substances. Seagrass is more ornamental but the Refugium or densely planted tanks require herbivores such as fish, marine snails, etc. to keep the stems free from epiphytic algae and predatory fishes to control the population of anthropods that could damage the vegetal tissues.



It looks like a strange thing, but Tridacne also helps to limit algae.

These gorgeous and expensive bivalves can effectively compete with algae for the same nutrients, limiting their development. The Tridacne performs excellent filtration work and also succeed in removing ammonia, nitrates and contributing to the reduction of phosphates and organic solvents, both food for plants. Some species such as T. Gigas, T. Derasa, T. Squamosa are large in size and may have a significant impact on the chemistry of water in a tank.


(Saving Clam Using The Glucose Method)


Corals compete with algae and algae compete with corals. In an aquarium with live rocks and few corals, the balance is difficult to maintain. The more corals there less probabilities for algae to prevail, while the less the number of corals the higher the ability of the algae to dominate.

How do corals control the growth of algae?

Corals produce substances that prevent algae from developing on the body surface. Porites, Sarcophyton, Lobophyton, Sinularia and many Gorgonie secrete a skin waxy film that is periodically renewed (also removing the spores that have adhered to), while other types of corals free abundant amounts of mucus to protect themselves from algae. Corals inhibit the growth of algae also by intercepting light. The expansion of coral tissue during the day produces shade reducing the development of algae.

Zoantides (Zoanthus, Palythoa, Protopalythoa) also contribute to limiting algal growth by expanding rapidly on rocks, occupying the spaces where algae may be, and secreting substances that partially inhibit algal growth. During the photoperiod the polyps expand by shading the intermediate spaces preventing the planting of plant filaments.

Tube Worms

Tube Worms such as those of the Bispira genus, whose presence is very common in marine aquariums set up with live rocks, reproduce by fission and can cling to the surface of the rocks. These worms use debris to fabricate their protective tubes and it is said that thanks to this system they are able to limit the development of algae.

Purified sweet water (Reverse Osmosis)

One of the first steps to controlling algae growth in aquariums is to limit the intake of nutrients. Tap water contains large amounts of nitrates, phosphates and silicates, and if it is not filtered properly it promotes algae growth. Reverse osmosis is obtained by treating the water through a system equipped with semi-permeable membrane, sediment filters, carbon and deionizing resins. It is important that osmosis water, used for evaporated water and for periodic water changes, is pure so as to avoid the proliferation of algae.


The end Third Part

Controlling the growth of algae in the aquarium Part 1

Controlling the growth of algae in the aquarium Part 2


Felice Panico
Acquariofilo dall'età di 10 anni con esperienza in acquariologia dolce,marina e salmastra, appassionato di immersioni subacquee e di microscopia.

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