Where health is concerned, diet is everything! This is as true for our fish as it is for us.  It would therefore seem logical to eat only the best foods we can obtain – and to feed only the best foods to  our precious captive fish. But do we truly know what we are eating or feeding? Or are we simply following the latest food and feeding trends?

Among the many foods available to the modern fish-keeping aquarist, one product stands head and shoulders above the rest: Spirulina!

Weird though the intertwining of you and your fish in my first paragraph may sound,  the truth is that I am promoting the use of Spirulina for both you and your fish! Because you can benefit from taking  Spirulina too!


Spirulina (actual name Spirulina Arthrospira) is a planktonic blue-green algae found in the warm waters of alkaline volcanic lakes. Spirulina is completely different from other algae in that it is more similar to bacteria than to plants. In truth it occupies a niche between bacteria and plants. (True plant plankton is toxic.) In fact, it is a unique kind of cyanobacteria, and its spiral shaped structure makes it look very similar to other cyanobacteria. Amazingly, it is this characteristic likeness to bacteria that causes the body, once it is ingested, to perceive Spirulina as a bacterium, and therefore causes it to step up its production of antibodies, which in turn increases disease resistance. 

But here is the true magic: Spirulina is rich in raw protein and seven major vitamins – A1, B1, B2, B6, B12, C and E. In fact, it is one of the best natural sources for vitamin B12. It also naturally contains beta-carotene and other colour enhancing pigments, as well as a whole range of beneficial minerals. In addition, Spirulina has a 62% amino acid content. It not only contains eight major amino acids, but also all essential fatty acids required for complete nutrition. Spirulina is also one of the most profound anti-oxidants available to us.

Unlike other green micro algae, like Chlorella, which have cell walls made of indigestible cellulose, just like green grass, Spirulina has a soft cell wall made of complex sugars and protein, and is therefore very easily digested. And because of its high content of usable and digestible amino acids, which are the building blocks of protein, Spirulina is nutritionally dense, yet five times easier to digest than the meat and soy proteins usually found in commercial fish foods.

Besides the above-mentioned high protein content and digestibility, Spirulina comes from waters with minerals deposited from ancient volcanic soils and mountains, where no other plants can survive due to the alkalinity caused by  this high mineral content. Yet,  Spirulina thrives in these alkaline waters, having evolved to incorporate and synthesize these many minerals and their derivative compounds into its cell structure. During this transformational process the minerals actually are chelated with amino acids, with the result that Spirulina renders the minerals in a natural organic form that is now more easily assimilated by the body of the organism that feeds on it.

This is extremely important in aquaria, because it is so difficult to supplement fish diets with the required minerals. Most fish foods are so low in natural calcium that added calcium is needed to  meet the requirements of the fish. Yet,  at the same time those supplements are usually inorganic and therefore incompatable – meaning that  the living body does not know what to do with these supplements and tend to excrete it, unused. In fact, the latest evidence seems to conclude that inorganic supplements can actually block the absorption of organic mineral forms, which can ultimately lead to mineral deficiency diseases.

But for all its magic, Spirulina’s most profound benefit must be that it improves immune function. This reason alone is why Spirulina should be part of EVERY fish diet, including carnivorous fish, which should be fed with Spirulina by gut-loading the worms, feeder fish, or crickets (arowanas) that make up their diet.

The reason is that Spirulina is rich in a brilliant blue polypeptide called ‘Phycocyanin’, a source of biliverdin which is among the most potent of all intra-cellular antioxidants. Studies also show that Phycocyanin beneficially affects the stem cells found in bone marrow. These stem cells are the ‘mother lode’ of all life, and the place from which both the white blood cells that make up the cellular immune system, and the red blood cells that oxygenate the body originate.

To understand Spirulina’s beneficial role in this, this, we need a short biology lesson.

All animals, including you and your fish, produce unconjugated biliverdin – a yellow coloured breakdown product of normal haeme catabolism, as a result of failing, or dying red blood cells. Haeme is the deep red, non-protein portion of haemoglobin in the blood that contains iron. Red blood cells (known as Erythrocytes), which have a 120 day life span, transport oxygen and carbon dioxide between the lungs and all the tissues of the body. In this sense we could say that a circulating red blood cell is little more than a container for haemoglobin. At the end of their life span, these red blood cells are broken down and converted to bilirubin and then carried to the liver by the plasma protein. Via several complex biological processes , bilirubin is eventually partly excreted in bile and urine, and partly re-circulated. On the other hand, elevated levels of billirubin may indicate certain diseases. Billirubin is, for example, responsible for the yellow colour of bruises, the yellow colour of urine (via its reduced breakdown product, urobilin), the brown color of faeces (via its conversion to stercobilin), and also the yellow discolouration we see in jaundice.

An enzyme called ‘biliverdin reductase’, converts the biliverdin to unconjugated bilirubin. The bilirubin quickly oxidizes back into biliverdin, and just as quickly biliverdin reductase recycles it back again into bilirubin. But why this endless to and fro? For the protection of the living organism! This form of bilirubin, (similar to the bilin in hemoglobin or bile), has been shown to be 10,000 times as powerful an antioxidant as is the glutathione used in anti-oxidant supplements. The unconjugated bilirubin is also a powerful inhibitor of NADPH Oxidase (nicotinamide adenine dinucleotide phosphate-oxidase). This enzyme is a major source of Super Oxide in any animal body, including yours and that of your fish, and is involved in dozens of degenerative processes involved in disease resistance and aging. End of the biology lesson.

Fact is that Spirulina supplements the amount of unconjugated biliverdin which the fish (or you and any other animals) are born with, providing profound protection from oxidative stress. Scientists also found that Spirulina not only stimulates the immune system through this above process, but actually enhances the animal’s ability to generate new blood cells.

Spirulina also has  anti-viral and anti-cancer abilities, because of a unique polymerized sugar molecule, called Calcium-Spirulan, which contains Sulfur and Calcium, both of which are important elements often missing from aquariums. Calcium-Spirulan prevents viruses from penetrating the body’s cell membranes and so stops it from infecting the cells, leaving the virus stuck and unable to replicate, until it is eventually eliminated via the body’s natural defenses.

Several studies have also shown that Spirulina, or its extracts can prevent or inhibit cancers in humans, animals, and fish. Some forms of cancer are the result of damaged cell DNA, causing  rapid and uncontrolled cell growth. Cellular biologists have now defined a system of special enzymes called Endonuclease, which repair damaged DNA to keep cells alive and healthy. When these enzymes are deactivated by oxidation, radiation or toxins, errors in DNA go un-repaired and cancer may develop. In vitro studies suggest that the unique polysaccharides of Spirulina enhance cell nucleus enzyme activity and DNA repair synthesis. This may be why several scientific studies, observing experimental cancers in animals, report high levels of suppression of several important types of cancer in the presence of Spirulina extracts.

Spirulina intake has also been found to prevent damage caused by toxins affecting the heart, liver, kidneys, neurons, eyes, ovaries, DNA, and testicles

Spirulina is a magic bullet, without doubt – and one from which both YOU and your fish can benefit. Moreover, it is a natural product!

So, let us look at the benefits of this product in more detail. Spirulina contains:

Protein:                  55%- 70%

Carbohydrates:  15% – 25% (an excellent low ratio for fish)

Fats (lipids):         6% – 8%

Minerals:               6 -13%

Fibre:                      8% – 10%

 Spirulina contains vitamins B1 (thiamine), B2 (riboflavin), B3 (nicotinamide), B6 (pyridoxine), B9 (folic acid), B12 vitamin C, vitamin D, vitamin A and vitamin E and Vitamin K.

 Natural beneficial and bioavailable Pigment Enhancers:

Phycocyanin (Blue): 14%

Chlorophyll (Green): 1%

Carotenoids (Orange/ Red): 47%

and also zeaxanthin, xanthophyll, echinenone, myxoxanthophyll, canthaxanthin, diatoxanthin, 3′-hydroxyechinenone, beta-cryptoxanthin and oscillaxanthin, plus the phycobiliproteins c-phycocyanin and allophycocyanin.

Important Trace Minerals (many of which are essential for proper electrolyte balance and osmotic function):

Calcium (1,315 mg/kg),


Phosphorus (15,400 mg/kg),














Essential Amino Acids:

 ISOLEUCINE (4.130/o): Required for optimal growth, nitrogen equilibrium in the body Used to synthesize other non-essential amino acids.

LEUCINE (5.8001o): increases muscular energy levels.

LYSINE (4.000/o): Building block of blood antibodies, strengthens circulatory system and maintains normal growth of cells.

METHIONINE (2.170/o): Vital lipotropic (fat and lipid metabolizing) amino acid that maintains liver health. An anti-stress factor.

PHENYLALANINE (3.950/o): Stimulates metabolic rate.

THREONINE (4.170/o): Improves intestinal competence and digestive assimilation.

 TRYPTOPHANE (1.1301o): Increases utilization of B vitamins, improves nerve health.

VALINE (6.0001o): Stimulates muscle coordination.

 This analysis brings me to the end of promoting Spirulina as a wonder food for you and your fish. What remains is a word of advice and a word of caution.

Spirulina should ideally form 60-70% of your fish diet, irrespective whether you are dealing with herbivores, omnivores or carnivores. None of these groups really stick strictly to the food-group labels they are given. A vegetarian may in fact occasionally feast on brine shrimp. A carnivore may indulge in vegetarian treats. Omnivores eat anything, but switch between one or other group as their needs dictate. Either way, carnivores are easily fed Spirulina by gut-loading their live food with Spirulina, as this mimics precisely what happens in the wild. Most carnivores obtain many of their most necessary alternative nutrients from the intestinal tracts of the fish they consume. Surprisingly, I have found that carnivores often will willingly take Spirulina in flake form if they see other fish eating it. Greed is a powerful factor, as is hunger. Fish not used to Spirulina may initially hesitate, or even refuse to eat it, but a fast for a day or two, plus the addition of a pinch or two of their usual food as a recognised ‘stimulant’ will soon acclimatise them to higher levels of Spirulina. Alternatively build the Spirulina content of your food portions up gradually, until you reach the required amount.

You may want to argue that you have used ‘this product’ or ‘that product’ for ages and that your fish are doing just fine! Yes, they may be, but believe me, it is the long run that counts – and they can do better! We can all survive on a singular diet of hamburgers and potato fries, but how good is it for us? At some or other time the bill for indulging in unwholesome food gets presented – usually in the form of some or other chronic disease, or a drastically weakened immune system.

My caution serves to remind you to read your fish food labels! There are many really excellent commercial foods on the market. Do not save in this respect. The health of your fish depends on what you feed them. The addition of Spirulina makes commercial fish foods more expensive, which is why the manufacturers avoid it. Thus, many products are marketed as ‘containing’ Spirulina, especially foods for vegetarians — but when you read those labels, you will often see Spirulina thrown in very low on the list, and in very small quantities!  A ‘Spirulina-based’ food should be just that – more Spirulina than anything else. If it is not, you need to add Spirulina to your fish diet, in quantities high enough to do the job! Even the best commercial foods contain no more than about 20% Spirulina. I would supplement spirulina even for these!

You will be rewarded with much deeper, more vibrant colouration in your fishes, better longevity, but most notably, a much lower incidence of disease!

Share this

Leave a Reply

Your email address will not be published. Required fields are marked *