A vial of phytoplankton

Phytoplankton Species and their individual Strengths

When purchasing live foods for your tank, many people simply take the shop employee’s advice when handed a jar of unidentified copepods for their reef tank. Most do not research into the different species of copepods, we just understand that they are a major element of our clean up crews and that our fish love snacking on them. But, what if you want to actually make sure you are getting the best option available, and not just whatever the local fish shop has in stock this week? Many aquarists turn to buy the copepods online for this reason, as online retailers typically understand the differences between species and explain them on each individual product’s page. After reading the pages of each individual species, many are left wondering “what do copepods eat?” Aside from detritus and fish food, most species we add to our tanks also eat algae and phytoplankton. But, there is also about a half dozen species of phyto available to hobbyists. Here, we will go into detail on each species and their benefits to your tank. These live foods can be added to your tank to do more than just feed microfauna. Phytoplankton in and of itself discourages nuisance algae growth and coral polyp extension and feeding!

phytoplankton under microscopeIsochrysis Galbana

Iso is a mobile alga, two flagella are used for locomotion. It is high in DHA (Docosahexaenoic Acid), which plays a major role in nervous system development. Fucoxanthin, a carotenoid found in these single-celled algae, is being found to make cancer and tumor cells undergo programmed cell death. In addition, Fucoxanthin was shown to reduce weight and decrease insulin resistance in animals diagnosed with obesity. And let’s be honest, we all have some fish that are a little chubby! Due to its nutritional value, it is one of the phytoplankton used to enrich copepods, Brine, mysids, rotifers, or other live foods to make them more beneficial to the consumers. Iso is also one of the most prominent feeds used in bivalve (such as clam) hatchery facilities due to its nutritional profile. So, this is a great option for feeding your tank! Nearly all bivalves, corals, and filter feeders will accept Isochrysis.


This is a genus comprised of 6 different species that can only be distinguished from one another by genetic sequence analysis. Because of this, most cultures contain more than one species of Nano. Unlike Iso, these algae are not mobile and can actually be found in fresh, brackish, and full saltwater environments. As such, freshwater clams and filter feeders can also benefit from the freshwater cultures of Nano. Nannochloropsis is able to accumulate huge amounts of astaxanthin, a pigment that improves red, yellow, and orange coloration. Zeaxanthin is carotenoid alcohol, and can also be found in Nano. It is also a pigment that enhances red, yellow, and orange colors. Spirulina is another source of this pigment. Finally, the pigment Canthaxanthin is also present in this phytoplankton. As with the other two substances, it enhances gold, yellow, and orange colors. Nano is also rich in EPA. Basically, this phytoplankton can help your livestock’s pink, red, orange, and yellow colors deepen and pop. Who doesn’t love naturally brilliantly colored animals?

Due to the fast-growing and quick reproduction of Nano, it can be added to the aquarium to hinder the growth of unwanted pest algae. It will easily outcompete these other species and is easily caught and consumed by all filter feeders, so it will not become a nuisance in and of itself. These properties, along with its three-month shelf life when refrigerated, make it a top choice for aquarists. So, what do copepods eat? Well, this phytoplankton may be one of the best options!

Tetraselmis Suecica

Tet is single-celled, motile algae. Although not as much information is easily available on this species, it is known to be rich in lipids, DHA, EPA, and arginine. Arginine is an important amino acid, as it is a neurotransmitter that aids in blood circulation. It also has a role in injury healing, removing toxins like ammonia from the body, and maintaining a healthy immune system. To keep your fish and inverts in top shape, it is easy to understand why an arginine-rich diet is beneficial. It is also one of the most carbohydrate-rich microalgae, which means it has more digestible glucose than other phytoplankton. Pods and other foods enriched with Tet are an easy addition to your feeding regimen that can keep your fish as healthy as possible!

Thalassiosira Weissflogii

Phytoplankton very magnified

Also occurring in fresh, brackish, and full saltwater, Thal is technically a diatom that is not motile. It can grow in less-than-stellar water conditions, including in chlorinated water! Iron, nickel, zinc, nitrogen, and silicates are all used by Thalassiosira, and these are limiting factors for its growth. This means if you discover that you have high metal concentrations in your tank through ICP or lab testing, adding Thal can greatly benefit your tank by removing these potential dangers. Due to the fact that it actively uses and depletes silicate in aquaria, it can be dosed to outcompete nuisance diatoms that grow over our sand and rocks. Thal is preferred by many filter feeders as it is larger in size than the other species on this list and can be used by older fry and larval invertebrates. And, individuals attach to one another and can form longer chains of Thal, so even the coarsest of filter feeders can utilize this species.

Closing Thoughts

As we can see from the above information, live phytoplankton has many benefits to offer your tank and livestock. If you find yourself wondering “what do copepods eat,” “what else can I feed my corals,” “how can I grow my pod population,” or “what are some natural defenses to nuisance algae” it may be time to look towards implementing a dosing regimen for phytoplankton. If you want to get the best bang for your buck, many companies are now offering mixed-species cultures to feed your livestock, so you get the benefits of each individual phyto. Some even include species not covered in this article, but these four types are some of the most prominent and beneficial ones available to hobbyists.

16 thoughts on “Phytoplankton Species and their individual Strengths”

  1. Jared Friedrich

    That is why I am ordering all my macro algae and copepods from you guys because I trust what you have in them. Scary pouring a jar of stuff into your tank when you really don’t know what could be in it

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