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Benefits of Feeding of Live Golden Fat Microalgae (Isochrysis sp.) to Reef Aquariums

An Introduction to Golden Fats

Microalgae are the most important class of primary producers we have on the planet. Through their photosynthetic magic, they are able to convert sunlight, nitrates, phosphates, trace metals and vitamins into the essential building blocks of life. Among the many important metabolites produced by microalgae, arguably the most important (outside oxygen) are lipids. Lipids are fats, but it is vital to know that not all fats are equal. Just like fuel, lipids store energy, but just as different fuels have different qualities, so do different lipids. Saturated lipids (butter) remain semi-solid at room temperature, while unsaturated lipids remain liquid even at lower temperatures (olive oil). Marine microalgae produce high yields of polyunsaturated fatty acids (PUFAs). I refer to these PUFAs as ‘golden fats’ because they are energy rich and extremely clean-burning (non-inflammatory). PUFAs are the vital metabolic currency which allow higher plants and animals to exist. Of these PUFAs, the Omega 3s Eicosapentaenoic acid (EPA) and Docosohexanoic acid (DHA) are the most integral for the proper development and operation of sensitive nerve cells such as those in the brain and eyes. Most terrestrial animals (including humans) have evolved to synthesize PUFAs from lesser fats and thus, do not need to eat PUFAs directly in order to survive. The same cannot be said for marine organisms which must directly consume golden fats in their diet in order to survive. This is a fact well-known to breeders of marine fish species, who can watch an entire batch of larvae starve to death if their live feed is not properly enriched with PUFAs.

Every marine critter derives its existence from the magic conducted by marine microalgae. Microalgae produce the world’s supply of golden fats, and without them, there would be no sharks, grouper, coral, lobsters or the like. Thus without a diet rich in golden fats, none of these animals can exist in captivity. All forms of aquaculture then, be them industrial salmon farms or ornamental reef tanks, are intimately dependent on global sourcing and distribution of golden fats. The aquarium industry largely sources its fats through massive forage fisheries. Forage fisheries are the industrial exploitation of species such as menhaden, sardines, anchovies or antarctic krill which are the primary/ secondary consumers of oceanic algal blooms. The algae are concentrated within the forage species, which are then caught and processed at a massive scale. The forage fish biomass is homogenized, dried and sold as ‘fish’/ ‘krill’ meal to feed manufacturers. Only a small percentage of PUFA remains stable through all that processing and aging, and a disastrous amount of energy is required to collect, process and distribute fish meal across the world. The need to expand aquaculture to feed a growing human population, has dramatically increased the cost of fish meal over the last decades. The answer to rising fish meal prices has been direct production of PUFAs through microalgal cultivation.

An Introduction to Tahitian Isochrysis and Its benefits to Reef Aquariums

Just like animals, microalgae can be selectively bred to enhance desirable characteristics. One such ‘domesticated’ algae species is Tahitian Isochrysis galbana. T-ISO was developed for increased PUFA production, and is to date one of the most widely utilized species in aquaculture. T-ISO was first employed for the commercial production of shellfish and shrimp larvae but is also used to enrich live feed species (rotifers, copepods, artemia) fed to larval fish. Because of this history, it is easy to imagine how dosing T-ISO benefits the reef aquarium: 

  • Small particle size (less than 10 microns), can fit into the tiniest of mouths!
  • Provides corals with direct source of golden fats (EPA/DHA), while at the same time, enriching copepods and other grazeables.
  • Each cell has a tail-like flagella it can use to remain in the water column - T-ISO can survive in reef conditions and thus uneaten cells do not immediately become waste.
  • T-ISO is a hungry nitrate and phosphate consumer and will extract excess nutrients from the water column until the cells are eaten.

With such considerations in mind, it is easy to imagine how a greater application of T-ISO golden fat algae may benefit the reef industry as a whole: 

  • Allow for the predictable keeping of finicky filter-feeding species (non-photosynthetic coral, tridacnid clams, electric scallops, feather duster worms, sea cucumbers etc.) 
  • Allow for the captive breeding of reef species which require algae or algal enrichment for larval development. 
  • Allow for the keeping/ captive breeding of new and novel species not previously available to the hobby due to limited survival/sourcing.
  • Allow for the sustainable production of fish-meal alternatives in order to lessen aquarium industry’s impact on wild fisheries.

In conclusion, golden-fat producing microalgae, like T-ISO, will become a growing asset to the reef aquarium community. There is a growing appreciation for feeding live microalgae to reefs because it is a way of delivering golden fats while reducing nitrate and phosphates. There is also a growing desire to make the reef industry more sustainable by lessening demand for wild fish-meal and increasing the amount of captive bred species available. Microalgae and their golden fats will be paramount to achieving such sustainability as the reef industry continues to mature.


Literature Consulted

Anthony K (2000) Enhanced particle-feeding capacity of corals on turbid reefs (Great Barrier Reef, Australia). Coral Reefs, 19, 59–67.

Hemaiswarya, S., Raja, R., Kumar, R. R., Ganesan, V., & Anbazhagan, C. (2011). Microalgae: a sustainable feed source for aquaculture. World Journal of Microbiology and Biotechnology, 27(8), 1737-1746.

Leal, M. C., Ferrier-Pagès, C., Calado, R., Thompson, M. E., Frischer, M. E., & Nejstgaard, J. C. (2014). Coral feeding on microalgae assessed with molecular trophic markers. Molecular Ecology, 23(15), 3870-3876.

Milione, M., Zeng, C., & Tropical Crustacean Aquaculture Research Group. (2007). The effects of algal diets on population growth and egg hatching success of the tropical calanoid copepod, Acartia sinjiensis. Aquaculture, 273(4), 656-664.

Migne A, Davoult D (2002) Experimental nutrition in the soft coral Alcyonium digitatum (Cnidaria: Octocorallia): removal rate of phytoplankton and zooplankton. Cahiers de Biologie Marine, 43, 9–16.

Moriarty, D. J. W., Pollard, P. C., Hunt, W. G., Moriarty, C. M., & Wassenberg, T. J. (1985). Productivity of bacteria and microalgae and the effect of grazing by holothurians in sediments on a coral reef flat. Marine Biology, 85(3), 293-300.

Mun, J. G., Legette, L. L., Ikonte, C. J., & Mitmesser, S. H. (2019). Choline and DHA in maternal and infant nutrition: Synergistic implications in brain and eye health. Nutrients, 11(5), 1125. Orejas C, Gili J-M, Arntz W (2003) Role of small-plankton communities in the diet of two Antarctic octocorals (Primnoisis antarctica and Primnoella sp.). Marine Ecology Progress Series, 250, 105–116.

Prostek, A., Gajewska, M., Kamola, D., & Bałasińska, B. (2014). The influence of EPA and DHA on markers of inflammation in 3T3-L1 cells at different stages of cellular maturation. Lipids in health and disease, 13(1), 3.

Singh, M. (2005). Essential fatty acids, DHA and human brain. The Indian Journal of Pediatrics, 72(3), 239-242.

Tamaru, C. S., Ako, H., Baker, A., Bybee, D. R., Brittain, K., & Nguyen, M. (2011). Growth and survival of juvenile feather duster worms, Sabellastarte spectabilis, fed live and preserved algae. Journal of the World Aquaculture Society, 42(1), 12-23.

Tzovenis, I., De Pauw, N., & Sorgeloos, P. (1997). Effect of different light regimes on the docosahexaenoic acid (DHA) content of Isochrysis aff. galbana (clone T-ISO). Aquaculture International, 5(6), 489-507.

Uthicke, S. (2001). Interactions between sediment-feeders and microalgae on coral reefs: grazing losses versus production enhancement. Marine Ecology Progress Series, 210, 125-138.

Taras Pleskun

Taras Pleskun

Taras is an aquaculture graduate student at University of Florida studying lipid production in microalgae. He aspires to aquaculture as many species as he can to demonstrate the necessity for the reef industry to move towards sustainable cultivation of its specimens. He hopes that one day, wild specimens are only collected as a means to bring novel species into the hobby.