Spirulina – super alga for aquarium fish

When choosing food for your aquarium fish, do you pay attention to its composition and look for formulas which contain spirulina because you know what an amazing ingredient it is? Or do you take the seller’s word for it or simply believe aquarists’ opinions that spirulina is a valuable part of the fish’s diet? I know this text is long. But the alga described here is called green gold for a reason. After reading it, you are unlikely to be surprised by anything regarding the use of spirulina in fish diets. Even the fact that it is a representative of cyanobacteria. You will also learn why spirulina is so often and readily used in aquarium fish foods.  

How did we discover spirulina?

In 1940, French phycologist Pierre Dangeard published information about a sample of interesting algae in the journal of the Linnaean Society of Bordeaux. The sample came from a market in a small village, Massakora, located about 50 km from Lake Chad. Dangeard claimed that these strange algae, called dihé  in the local language, were part of the local people’s diet. They were harvested from small lakes and ponds located around Lake Chad. The green and blue algae floating on the surface of the water were fished out and dried. Microscopic analysis carried out by the Dangeard revealed them to be filamentous, spirally twisted algae.   

This information received very little attention in the scientific world, though, probably due to the outbreak of World War II. Europe had to wait 25 years for further reports on spirulina, when the rediscovery of dihé  was made by the botanist, Jean Léonard. He confirmed that the green dry “cookies” available in the local market consisted mainly of spirulina extracted from numerous lakes around lake Chad with alkaline and highly saline water.

At the same time, another species of spirulina, Spirulina maxima, was found across the Atlantic, in Lake Texcoco.  Although it was not used as a human food in Mexico at that time, historical records from the Spanish Conquest period indicated that it was a component of the Aztec diet. Spanish people mentioned in their notes tecuitlatlcookies. The local people baked from a substance resembling blue-green sludge pulled from the lake with dense nets.

Is spirulina cyanosis?

Spirulina was first isolated by P.J. Turpin in 1827 from a sample taken from a stream, and thus it was scientifically identified even before Dangeard’s reports. Originally, these organisms, which are capable of performing photosynthesis, were classified as algae, a very large and diverse group of thallophytes (not having tissues or organs). It is worth mentioning that algae are a morphological-ecological (rather than systematic) grouping of organisms that are not related to each other.  

Since 1974, spirulina began to be classified in theCyanobacteria division (cyanobacteria). Now Cyanobacteria (as a type) are included in the Bacteria domain. Domain is a systematic category higher than kingdom, introduced in 1990 as the category with the highest taxonomic rank. This systematic approach is now increasingly popular. Three domains were created:

• domain: Eukaryota (all nuclei),
• domain: Archaea (single-celled organisms known from extreme habitats, such as geysers),
• domain: Bacteria.

Type: Cyanobacteria.

Note, however, that we still like to call spirulina an alga in everyday language, rather than a cyanobacteria.

Spirulina or Arthrospira– which name is correct?

The algae discovered by P.J. Turpin were in the form of filaments, with no transverse septa dividing cells. Following the isolation of species that possessed such septa, Stizenberger created the genus Arthrospira in 1852. Over the ensuing years, there had been an ongoing debate about the validity of this division. Until it was discovered that the species of the genus Spirulina also possessed such transverse septa. It turned out that researchers had not had the proper apparatus to spot them earlier. The new possibilities that scientists gained from year to year meant that more differences between these organisms began to be discovered. This, of course, triggered further discussions on systematic classification.

Now we know that we are dealing with two distinct types: Spirulina and Arthrospira. And it is the latter type that includes species that have health-promoting properties and are used as food. Therefore, it is worth remembering that the correct species names of organisms used in the composition of products with “spirulina” in the name are Arthrospira platensis and Arthrospira maxima.

On the other hand, the name “spirulina” will probably stay with us for good. It is widely used in the cosmetic, pharmaceutical and pet industries. It is recognized by the customers and carries positive connotations.  

Occurence of spirulina

Arthrospira platensis occurs naturally in Africa, Asia and South America, while Arthrospira maxima can be observed in Central America. The fact that spirulina was included in the diet of people living in the area of lakes Chad and Texcoco is related to the specific conditions of the reservoirs from which it was harvested. Collected and dried green mats contained almost exclusively Arthrospira platensis or Arthrospira maxima cells. This should not be surprising if you look at how extreme conditions these organisms can live in. The water of the lakes from which it was fished was characterized by significant salinity (> 30 g/l), caused mainly by carbonates and bicarbonates, and high pH (8.5-11 pH). Such water parameters do not encourage the growth of other cyanobacteria or algae that could pose a threat to the health and even life of humans and animals.  

Spirulina as a source of protein

Initially, the main reason for the interest in spirulina was its extremely high protein content, which ranges from 55% to 70%. This is impressive value compared to the protein content of meat (15-25%) or soy (35%). In addition, spirulina protein was found to be more valuable than legume protein and only slightly inferior to milk or egg protein (it contains fewer amino acids such as cysteine, methionine and lysine).

This high protein content was so promising that studies were initiated on many species of fish intended for consumption. They were fed with feeds containing 1 to 100% spirulina. The effects were varied. In some fish, such as Nile tilapia (Oerochromis niloticus) and carp (Cyprinus carpio), a significant effect on growth has been observed. While in others, such as the African catfish (Clarias gariepinus), high doses of spirulina slowed their growth. On this basis, the thesis was put forward that carp or tilapia, which prefer a significant share of plant components, are better adapted to utilize spirulina due to their appropriate digestive enzymes.

Does Spirulina have a colour-enhancing effect on fish?

Carotenoid content in spirulina dry matter is estimated at 0.5%. Beta-carotene dominates (0.2-0.4%). These are very high values. However, the concentration of carotenoids alone is not everything! W should bear in mind that colour-enhancing effect also depends on the species of fish, the frequency of food intake and spirulina dosage. Some species with the ability to convert b-carotene to astaxanthin will intensify their coloration better and faster compared to fish that do not have this ability.   

Rainbow trouts needed only 2.5% spirulinam in their food to significantly increase the concentration of pigments in their skin (24.98 µg/g dry weight, compared to a control group of 9.05 µg/g). In contrast, color enhancement in koi occurred at 7.5% spirulina, and in  Metriaclima lombardoi and Pseudotropheus acei cichilds – at 20% spirulina in the food. An example of a fish in which spirulina did not improve coloration would be the red porgy (Pagrus pagrus). It is a fish intended for consumption that lacks the ability to convert b-carotene to astaxanthin.

Spirulina improves fish’s immunity

Immunoactive components contained in spirulina stimulate the activity of cells that conduct phagocytosis (foraging cells). Moreover, they increase the production of lysozyme (a protein that breaks down the cell wall of bacteria, it is one of the mechanisms of non-specific immunity). They also increase the antimicrobial activity of fish mucus and increase the number of white blood cells, whose task is to protect the body from bacteria and viruses. All this is confirmed by numerous scientific studies involving fish.

It is also worth remembering about carotenoids and other assimilation pigments of spirulina (chlorophyll and phycobilins). These compounds also have many important physiological functions, including stimulation of the immune system. Chlorophyll for instance has a pronounced bacteriostatic effect and spirulina contains as much as 0.8-1.5% of chlorophyll (by dry weight), which gives it a leading position among other organisms. And blue and red phycobilins, like carotenoids, have strong antioxidant properties. They effectively protect fatty acids and other valuable compounds from free radicals.

Spirulina supports reproduction of aquarium fish

The active ingredients of spirulina also include unsaturated fatty acids. Spirulina contains high amounts of linoleic acid and gamma-linolenic acid, which are precursors to arachidonic acid. It is arachidonic acid that has an important function in fish reproduction. The importance of these acids was shown in an experiment in which two-spotted gurami(Trichopodus trichopterus) were given food containing 2.5%, 5.0%, and 10% spirulina. The higher dose of spirulina in the food reduced the time needed for first spawning by about 12 days compared to the control group. Pseudotropheus acei cichlids that received as little as 2.5% spirulina in their feed produced significantly more eggs compared to the control group. The positive effect of spirulina on reproduction of some fish species is attributed to its specific components. These include essential fatty acids, vitamins C and E, and carotenoids.

Is spirulina safe for aquarium fish?

Many species of cyanobacteria have been attributed with toxic effects on living organisms. Spirulina as a representative of this group of organisms also raised doubts at first. Many studies have been carried out to resolve them and prove that it is not toxic to living organisms. These studies involved a variety of animal species, including fish, and were often conducted on several generations. Scientists evaluated the overall condition of the animals and their reproduction. In-depth histopathological studies were also performed. They did not show any toxic effects of spirulina on living organisms, regardless of the dose used. Positive research results allow to use spirulina on a large scale both in animal and human nutrition.

Choose aquarium fish food with spirulina

Tropical offers several foods for ornamental fish, where spirulina is an important ingredient. You can choose between flake foods, granules, chips, tablets and discs with spirulina content ranging from 6% to 36%.

Super Spirulina Forte is a family of foods with as much as 36% spirulina, Here you will find 5 different forms of food that will easily feed fish of different sizes and feeding patterns. If you want to learn more about choosing the right form, see How to choose food for aquarium fish?

Try Super Spirulina Forte, Super Spirulina Forte Granulat, Super Spirulina Forte Mini Granulat, Super Spirulina Forte Chips, Super Spirulina Forte Tablets

If you have bottom-dwelling fish, especially herbivorous Loricariidae, choose foods in the form of tablets, wafers or discs. Among them, I particularly recommend these with high content of spirulina (36%): Hi-Algae Discs XXL, Hi-Algae Discs, Pleco’s Tablets.

For lovers of herbivorous and omnivorous cichlids from Africa, I have an interesting offer in the form of soft pellets in two sizes Soft Line Africa Herbivore S and Soft Line Africa Herbivore M. In these products the spirulina content is 20%.

Aquarists who like to experiment should necessarily reach for the Gel Formula for Herbivorous Fish, which contains 25% spirulina. This product allows you to create natural feeding grounds for fish. You just have to spread the prepared mixture on the stone and put it in the refrigerator. Once the mass has concentrated, you place the stone in the aquarium and observe the behavior of your fish. You can read more about jelly foods in Sofr Gel food for fish.

Benefits for fish from the use of foods with spirulina

If you are here, it means that you found the material I prepared for you interesting. Do you remember the question in the first paragraph? Why is spirulina so often and readily used in aquarium fish foods? I think you know the answer now. However, let’s sum it up. Spirulina is a super alga, or cyanobacteria if you prefer, which clearly affects the health and condition of fish. Using fish food rich in this ingredient, the following benefits can be observed:

• increased disease resistance,
• intense coloration,
• steady growth and development,
• healthy digestive system.

dr inż. (Ph.D.Eng) Aleksandra Kwaśniak-Płacheta