How Marine Phytoplankton is Grown

The way your marine phytoplankton supplement was produced matters at least as much as what species it contains. Two products listing Nannochloropsis on the label can deliver meaningfully different nutrient profiles depending on whether the algae were grown in a sealed facility or an outdoor pond. You cannot see those differences on a label, but you will find them in an independent test report.

Most supplement brands do not tell you how their phytoplankton was cultivated. That silence is worth noticing. We grow ours in closed photobioreactors using filtered water, and this article walks through each stage of that process, from the laboratory flask to the finished powder, so you can judge what separates careful production from volume production.

Starting a Marine Phytoplankton Culture

Every production batch begins in a laboratory, not in the bioreactor itself. A starter culture of Nannochloropsis gaditana is maintained under controlled conditions and scaled up through progressively larger vessels until it reaches the volume needed for the photobioreactor. Reputable producers verify species purity at each transfer stage because contamination introduced early is the hardest kind to detect later.

If that sounds fussy, consider the alternative. In open-pond cultivation, airborne organisms, wind-carried spores, and waterborne bacteria can enter the culture freely from the moment production begins. You would not notice the contamination by looking at the finished powder. You would only see it in a heavy metal report or a microbial assay, and most products do not publish those.

Why the Inoculation Stage Matters for Your Supplement

The stepwise approach is not about caution for its own sake. It is about ensuring that what enters the bioreactor is exactly the organism intended, with no competing species along for the ride. When a culture is not properly verified before scale-up, the batch still produces biomass, but the nutrient profile drifts because a faster-growing contaminant has outcompeted the target species.

If you are reading a product label and it does not name the species, that is a signal. A producer confident in their culture work names the organism. Silence on species identity often means the supply chain is opaque enough that species-level verification did not happen at the start.

Growing Marine Phytoplankton in a Closed Photobioreactor

The bioreactor itself is a sealed system of transparent tubes through which the culture circulates. Filtered water provides the growing medium. CO2 is fed in as the carbon source for photosynthesis. Light intensity, temperature, pH, and nutrient concentrations are monitored and adjusted throughout the growth cycle.

Walk into our facility and what you see is metres of clear tubing filled with a green suspension that deepens in colour as the culture matures.

This is not a set-and-forget arrangement. The culture's EPA content, pigment production, and growth rate all respond to the growing conditions. Published data shows that lower light intensities (around 75 µmol/m²/s) favour higher EPA content as a proportion of dry weight, while higher intensities grow more biomass faster.

The optimal temperature for EPA productivity in N. gaditana is roughly 25°C, yielding about 30 mg EPA per litre per day. In well-run facilities, these variables are monitored continuously because the goal is not just biomass but biomass with the right nutritional profile.

Biomass-Optimised vs Nutrient-Optimised Phytoplankton Cultivation

A batch that grows quickly but produces less EPA than expected is not a good batch, even if it looks fine in the tube. That distinction matters to you because it determines whether the finished product delivers the EPA milligrams declared on the label. Volume-optimised cultivation maximises how much algae you harvest. Nutrient-optimised cultivation maximises what that algae is worth once it reaches your kitchen counter.

The difference is invisible in the powder. You cannot smell it, taste it, or see it. You can only verify it through a certificate of analysis that reports the actual EPA content per batch. If a brand does not offer batch-specific testing data, you are trusting the label without verification.

How the Harvest Window Affects Nutrient Density

The harvest window matters more than most production descriptions acknowledge. Too early, and the EPA and carotenoid content may not have peaked. Too late, and the culture begins to degrade. Both carotenoid pigments and long-chain fatty acids follow a curve: they accumulate during active growth, plateau, and then decline as the culture enters stationary phase. Missing the plateau means lower potency in the finished product.

Quality-focused producers time the harvest based on monitoring data, not on a fixed calendar. That is what separates nutrient-optimised production from volume-optimised production. You cannot see this decision on a product label, but it affects the nutrient profile of every capsule or scoop you take.

Once monitoring indicates peak conditions, the biomass is separated from the growing medium by centrifugation or filtration, then moved immediately to drying. Speed matters here. Leaving wet biomass sitting degrades the fatty acids and pigments you are paying for.

Why Drying Method Matters for the Finished Product

Heat is the enemy of EPA, carotenoids, and other heat-sensitive compounds. A study on Nannochloropsis oceanica found that spray-dried biomass lost roughly 70 per cent of its EPA through biohydrogenation, compared to 45 per cent for freeze-dried biomass from the same culture. That is not a subtle difference. It means the drying method can determine whether the EPA on the label matches the EPA in the powder.

If you have ever compared a cheap phytoplankton powder with a premium one and noticed the colour difference, drying method is a likely explanation. Intact carotenoids produce a deep, rich green. Heat-damaged biomass looks duller and more olive-toned.

Gentle drying methods preserve the fatty acid and pigment profile. The trade-off is straightforward: gentle drying is slower and more expensive than industrial blast-drying. A producer optimising for throughput and cost will choose the faster method. The nutrient profile absorbs the consequences, and your body receives less of what the label declares.

You will not find "drying method" on most supplement labels. We consider it one of the largest hidden variables in the finished product's nutritional value, and it is worth asking about directly.

How Every Phytoplankton Batch Should Be Tested for Purity

After drying, reputable producers test every batch through independent laboratories for heavy metals (lead, cadmium, arsenic, mercury), microbial contamination, and nutrient potency. The results should be linked to the batch number printed on the product packaging, which means you can request the specific data for the specific tub sitting in your cupboard.

Independent verification is the minimum standard you should expect from any supplement you put in your body. We consider it non-negotiable for any product that enters your daily routine. A product that has not been independently tested is a product whose label you are taking on faith. If you ask a brand for their testing data and they cannot provide it, that tells you something about their production process.

What to Look for in a Phytoplankton Test Report

When you read a certificate of analysis, check three things. First, confirm that heavy metal levels (particularly lead and cadmium) fall below the limits set by EU food safety regulations. Second, check that the microbial counts are within acceptable ranges.

Third, verify that the EPA content per serving matches what the label claims. If any of these are missing from the report, or if the report is not batch-specific, the testing is not as thorough as it should be.

Why Photobioreactor-Grown Phytoplankton Costs More

Sealed infrastructure, laboratory-grade starter cultures, continuous monitoring, gentle drying, and independent batch testing all cost more than growing algae in a pond, drying it fast, and bagging it. We are transparent about this: if you are comparing two phytoplankton products and one costs noticeably less, the production method is usually the explanation.

What the Price of Your Phytoplankton Supplement Reflects

The price of ULTANA Phytoplankton reflects each of these production steps. That is not a justification for expense. It is an explanation of where the money goes. A cheaper product is not necessarily worse, but the question worth asking is which steps were shortened or skipped to reach that price point.

You can reverse-engineer a production process from the price and the available documentation. A product that costs half the price of a photobioreactor-grown alternative and publishes no batch testing data is telling you, through omission, what its production looks like.

Marine Phytoplankton Production FAQ

Does it matter whether phytoplankton is grown in filtered water or seawater?

It matters for purity. Seawater introduces whatever is in the local marine environment, including heavy metals, microplastics, and microbial contaminants. Filtered water gives the producer control over what enters the culture. We chose filtered water for our ULTANA range for exactly this reason. If a product does not state its water source, it is worth asking.

Can you tell the difference between open-pond and photobioreactor phytoplankton?

Not by looking at the powder, tasting it, or smelling it. The differences show up in independent testing: heavy metal levels, microbial counts, and batch-to-batch consistency. If a brand does not publish testing data, you have no way to assess cultivation quality from the product alone.

Why do some phytoplankton supplements cost so much more than others?

The production method accounts for most of the price difference. Photobioreactor cultivation, gentle drying, and independent batch testing add cost at every stage. Open-pond cultivation, industrial drying, and minimal testing reduce it. The cheapest product on the shelf is not necessarily unsafe, but the question is whether the production shortcuts that enabled that price affected the nutrient profile you are paying for.

How do you know the EPA content on the label is accurate?

You verify it through a certificate of analysis tied to your batch number. If a brand offers batch-specific testing data from an independent laboratory, that is the strongest evidence. If the brand does not offer this, the label claim is unverified. Ask the brand directly for batch-specific documentation before you buy.

This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Consult your GP before starting any supplement.

Methodology and Disclosure

Phytality manufactures marine phytoplankton supplements from Nannochloropsis gaditana grown in closed photobioreactors. We have a direct commercial interest in this ingredient and in the production methods described.

Claims about EPA sensitivity to heat and drying conditions are supported by published literature on lipid oxidation in microalgae (Ma et al., 2016; Zanella and Vianello, 2020). The techno-economic comparison between open-pond and photobioreactor cultivation draws on Chauton et al. (2015). Contamination risks in open-pond systems are documented in Vega et al. (2020).

Last reviewed: March 2026. Next review due: March 2027.