Phytoplankton For Dogs: Benefits, Dosage & More

Phytoplankton for dogs is still a niche supplement—but interest is growing, especially among raw feeders looking for sustainable marine nutrients.

Rich in naturally occurring Omega-3s, antioxidants, and trace minerals, marine phytoplankton is often marketed as a concentrated alternative to fish or fish oil.

I’m Barbara, the founder of K9sOverCoffee, and I’ve been feeding raw dog food since 2015.

This article was inspired by a newsletter reader question from Alisson, who asked whether phytoplankton can replace fish in a raw dog food diet—and if so, how much to use.

So in this guide, I’ll break down what phytoplankton can (and can’t) do for dogs, how to dose it responsibly, and how it compares to other popular marine supplements. In this article, you’ll learn:

• What marine phytoplankton is and how it fits into a dog’s diet
• The benefits of phytoplankton for dogs, including omega-3 and antioxidant support
• Whether you can use phytoplankton instead of fish in raw dog food
• Phytoplankton dosage for dogs, with practical guidelines
• The difference between phytoplankton and kelp for dogs
• How phytoplankton compares to spirulina
• Where to buy high-quality phytoplankton for dogs

The goal is to help you decide if phytoplankton makes sense as a dog supplement for YOUR dog—not to oversell it as a replacement for whole, species-appropriate foods.

Phytoplankton For Dogs

First things first, phytoplankton are microscopic algae that are about 9 times smaller than a red blood cell!

They’re primarily associated with marine life, and all ocean animals rely on it, including fish.

Important to understand: Phytoplankton is not fish, but it’s what fish eat!

That said, there are certain types of phytoplankton that are beneficial for dogs (and humans!) as a nutritional supplement.

Specifically, marine phytoplankton, such as Nannochloropsis gaditana and Thalassiosira pseudonana.

Marine Phytoplankton Benefits For Dogs

Marine phytoplankton is rich in essential nutrients, including Omega-3 fatty acids (mostly EPA = Eicosapentaenoic acid, but also some DHA), amino acids, Vitamins E & C, trace minerals, antioxidants, chlorophyll, and other bioactive compounds.

These nutrients nourish the cells directly without having to be digested, and help support various aspects of your dog’s health, including:

1. Healthy skin and coat: The Omega-3 fatty acids in phytoplankton contribute to a shiny coat, reduce inflammation, and alleviate certain skin conditions like excessive itching and shedding.
2. Joint health: Phytoplankton’s Omega-3 fatty acids have anti-inflammatory properties that help reduce joint inflammation and support overall joint health.
3. Immune system support: The vitamins, minerals, and antioxidants found in phytoplankton can help boost your dog’s immune system and protect against oxidative stress.
4. Energy and vitality: Phytoplankton’s nutrient profile contributes to improved energy levels and overall vitality in dogs.

Keeping all that in mind, it’s essential to choose high-quality, human-grade phytoplankton supplements.

Next up is where you can find these!

Where To Buy Phytoplankton For Dogs

The following products include 100% pure phytoplankton, and you can use them both for your dog as well as for yourself and your human loved ones:

• Mr Ros Marine Phytoplankton (from the Netherlands)
• Holistic Bin Marine Phytoplankton Powder (from the Netherlands)
• MySuperfoods Marine Phytoplankton Powder (from Portugal)

Can I Use Phytoplankton In Place Of Fish for Dogs?

As you may know if you’ve read some of my raw dog food blog posts, I add whole fish to Wally’s raw meals – and also to my Lab puppy Pepper’s raw meals, of course.

Specifically, mackerel and herring.

That said, I use phytoplankton when I’m out of frozen whole fish for Wally. The kind I buy here in Germany is from the Netherlands.

So yes, you can replace fish or fish oil with phytoplankton.

And if your pup is allergic to fish in general, you can try giving them phytoplankton instead.

Phytoplankton For Dogs Dosage

Since phytoplankton has double the amount of Omega-3s than fish oil, dogs only need very little of it on a daily basis.

According to Dogs Naturally Magazine, you can give any sized dog 1/16 of a teaspoon worth of phytoplankton.

You can either use a 1/8 teaspoon and divide it in half to get to 1/16 of a teaspoon.

Or you can fill a 1/4 teaspoon with phytoplankton, then divide it in half, and divide one half in half again.

FYI: 1/16th of a teaspoon is considered a pinch.

I’ve also found slightly more detailed daily dosage instructions on the packaging of Mr. Ros Marine Phytoplankton for dogs:

• 1/16 teaspoon for small dogs
• 1/4 teaspoon for medium dogs
• 1/2 teaspoon for large dogs

I personally use this approach when I measure out Wally’s phytoplankton allowance.

That’s because it makes sense to me to make the amount you feed dependent on your dog’s weight.

Since Wally’s a medium size dog and weighs in at around 38 lbs, he can have 1/4 teaspoon of daily phytoplankton.

But only when his meals don’t feature any raw fish!

What’s The Difference Between Phytoplankton and Kelp for Dogs?

Now, both kelp and phytoplankton are important marine organisms, but they differ in terms of nutritional composition and the roles they play in marine ecosystems.

Phytoplankton

Phytoplankton are microscopic, photosynthetic organisms that mostly float in the ocean and are the foundation of marine food chains.

These organisms are responsible for a significant portion of the Earth’s oxygen production through photosynthesis.

Phytoplankton is a primary source of marine nutrients including Omega-3 fatty acids, and plays a crucial role in supporting marine life, including fish.

Kelp

Kelp is a type of large brown algae that grows in underwater forests along coastlines.

It’s very nutritious and contains various vitamins, minerals, and dietary fiber.

Kelp is also very rich in iodine, which is important for thyroid function, as well as other minerals like potassium, calcium, and magnesium.

The biggest difference between the two is that phytoplankton is richer in Omega-3 fatty acids, and kelp is richer in iodine.

...And What About The Difference Between Phytoplankton and Spirulina?

Because the two look pretty much identical, don’t they?

Well, phytoplankton only grows in oceans (saltwater), and spirulina only grows in freshwater.

Also, phytoplankton is more nutrient dense, but spirulina is said to help neutralize a dog’s bad breath and coat smell!

Phytoplankton For Dogs: Bottom Line

Phytoplankton is a nutrient rich microscopic algae, which makes it a superfood for dogs (and their humans)!

You can add it to your dog’s (raw) dog food instead of whole fish or fish oil. The really good news is that you can actually give it to dogs who don’t do well with fish!

While it’s a bit more on the expensive side, it lasts a while since dogs only need very little of it.

I personally enjoy eating fish, but I’ll also add some phytoplankton to my goat yogurt, along with a variety of nuts and fresh fruit.

For more raw feeding resources, visit my full homemade raw dog food library.

Related Reading:

• Difference between mackerel and herring
• The benefits of kelp for dogs + recipes
• All about raw fish for dogs

Barbara Rivers

Barbara Rivers is the founder of K9sOverCoffee and a raw feeding educator with over a decade of hands-on experience.

She has fed raw in the US and Europe since 2015, after her Boxer mix Missy’s cancer diagnosis led her to move away from processed kibble and commit to species-appropriate nutrition.

As a former professional dog walker, she developed deep insight into canine behavior, conditioning, and the essential link between proper exercise and long-term health.

Barbara completed online training with veterinarian Dr. Marion Smart and Labrador breeder Dana Scott and works for one of Germany’s leading raw dog food brands, BARFER’S.

In 2026–2027, she is completing a year-long raw nutrition certification for dogs and cats at THP School, founded by raw feeding pioneer Swanie Simon.

Through her blog and weekly newsletter, she provides clear, experience-based guidance to help dog owners feed raw safely and confidently.