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Spirulina 101


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For years now spirulina has been promoted as the 'best' food for herbivorous fish, and as a color enhancing agent second to none. While it can be a high quality ingredient used in a fish food formula, there is a reason why no major fish food manufacturer has created a staple food for cichlids that is 100% spirulina. Most of the fish food currently marketed as "spirulina" formulas, are in fact fish meal based, with an inclusion rate 2-30% spirulina, and green dye used to create a veggie look to the food.

Vitamin A is required by all fish, but certainly not in the levels found in Spirulina.

As an example, studies show that juvenile Rainbow Trout require approx 2,000-2,500 IU/KG of vitamin A for optimum health. A Carp requires approx 1,000-2,000 IU/KG. Spirulina contains approx 23,000 IU per 10 grams, which equates to 2,300,000 IU/KG. In each heaping tablespoon of pure spirulina flakes, there's approx 23,000 IU of vitamin A. That's 460% of the US Daily Value recommended for an adult human!

Vitamin A is one of the fat soluble vitamins, so when dietary intake exceeds metabolic demand, those vitamins accumulate and get stored by a fishes body, not excreted such as water soluble vitamins. Over time this can lead to what's known as hypervitaminosis.


Hypervitaminosis A has been described in fish and in other animals and involved enlargement of liver and spleen, abnormal growth, skin lesions, epithelial keratinization, hyperplasia. of head cartilage, and abnormal bone formation resulting in ankylosis and fusion of vertebrae. Hypervitaminosis A is reflected in very high liver oil vitamin A content and elevated serum alkaline phosphatase

In salmonids, you can refer to the following paper for toxicity levels of vitamin A. (Hilton, 1983; Poston et al, 1966; toxic level of vitamin A, 2.2–2.7 million I.U./kg diet)

I believe that would put any pure spirulina flakes right smack dab in the toxic level ball park. If that level has been determined to be toxic for salmon, then I think it's safe to assume that it won't be very user friendly for cichlids, either.

If that wasn't bad enough, Spirulina contains zero (0) vitamin C.

Just like humans, the vast majority of fish lack the ability to make their own vitamin C, so it must be supplied via their diet. In salmonids, a vitamin C deficiency will result in one or more of the following symptoms: reduced growth, impaired collagen formation, scoliosis, lordosis, internal/fin haemorrhage, dark colouration, distorted/twisted gill filaments, poor wound repair, increased mortality, reduced egg hatchability.

With regards to vitamin C, according to aquatic animal nutritionist Dr. Juli-Anne Royes Russo Quote:

"Studies have shown that the general requirements for fish are between the ranges of 10 and 500 mg/kg of diet for adequate growth and an absence of spinal deformities".

(Aquarium Fish Magazine - Sept 2005)

Her credentials can be found here: http://www.hswri.org/research/scientistDisplay.cfm?sciID=66

Most commercial fish feeds contain 150-200 mg/kg of vitamin C.

Just in case anyone thinks that I'm pulling those spirulina numbers out of thin air:


I've cross referenced much of the info in the link above, and those numbers appear to be accurate.

Spirulina is also low in some of the essential amino acids, I don't believe that it has anywhere near the Omgea 3 levels that are found in most fish meal based foods, nor does it have the UP (usable protein) level that a quality fish meal has. For the latter I'll use a spirulina marketing/sales website as a reference for comparison. http://www.spirulinasource.com/earthfoodch2a.html

If you scroll down to chart 2.5 .... Net protein utilization and usable protein

you'll find that the UP of spirulina is 40%. (using 65% protein for spirulina) Now if we take a high quality fish meal, such as Herring meal, which is approx 75% protein, then the UP becomes 60%, which is significantly higher than spirulina. This is due to Herring meal having a much higher Net Protein Utilization (NPU) value.

Taking all of the above into account, this is exactly why no fish manufacturer in their right mind would produce a fish food designed as a staple food, that was 100% spirulina, or for that matter, even based on spirulina. (as in the main ingredient)

To do so would fly in the face of everything that experts in the field of fish nutrition have learned over the past 50 years. Real experts, people who have dedicated their life to the study of nutritional disorders & disease in fish.

Is high quality spirulina a useful raw ingredient for fish food, yes! But it's inclusion rate for color enhancement & overall nutritional benefits (at least with most species) needn't be more than 3-5%.





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thx mate!

very interesting read indeed....

in the past i would have fed my tropheus 100% spirulina foods if i could get my hands on it....luckily for them there are none available in Australia..

i think the cruz of it all is NLS contains everything u would ever need for your fishes nutritional requirements.....an no, i don't work for Waruna!!! :thumb

That Neil is a legend and really does his homework...no wonder he has won so many over to NLS foods!!!

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