Spirulina 101

[RD.]

I've sat on some of this info for a while, only because I felt that if I posted it on an online forum there would be those that would feel it was yet another rant from RD. (the nutrition mad man!)

I'm certainly no expert (on anything) but I don't feel that one has to be an expert to understand the info supplied below. Spirulina is indeed a great food for fish, but its inclusion rate in a feed should be limited. Somehow over the years spirulina has become somewhat of a holy grail of fish foods, with manufacturers jumping on the bandwagon & ceasing the moment for all it was worth. Out came the green dye & every company & their dog created a new "spirulina" formula.

I have no problem with spirulina as a raw ingredient in a fish food, but I shudder every time that I read someone suggesting to another fishkeeper that they should be feeding large amounts of spirulina to their fish. Any decent quality fish food will already contain spirulina, and in an amount that will enhance the health of your fish, not place its health in harms way.

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 (or any species) 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 ornamental species, 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

"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, although some brands do contain higher amounts.

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

http://www.spirulina.com/SPBNutrition.html

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%.

HTH

[Jeff M]

Good article Neil. I always wondered why on flakes and discs labelled spirinula that the main ingredient wasn't spirinula. This now puts it in a little better perspective.

Jeff

[RD.]

Jeff - for the most part these products sold as "spirulina" formulas are nothing more than a marketing gimmick.

I recently had someone tell me that they used the product listed below as a "spirulina supplement" to boost the amount of spirulina found in their main staple food.

This product is sold as a Premium Spirulina Flake.

Ingredients: fish meal, soy flour, wheat flour, oat flour, corn gluten meal, dried spirulina algae, shrimp meal, dried plankton, brewers dried yeast, soy oil, lecithin, vitamin supplements, natural coloring, ascorbic acid, artificial coloring.

If you add up the soy flour, wheat flour, oat flour, and corn meal, take a guess what the main ingredient in this food actually consists of.

The ironic part is this persons main staple fish food contained more than an adequate amount of spirulina, and as much or more than what is found in the formula above. (without all the excess grains!) The only difference - their main staple didn't market the food as a "spirulina" formula, and this particular manufacturer didn't use green dye (artificial coloring) in an attempt to fool consumers into believing their product was veggie based.

The laws for ornamental fish food are rather lax, and the reality is that manufacturers can get away with things that would never be allowed in dog and/or cat food products.

Edited July 7, 2006 by RD.