Algae vs Fish Oil: Which is Better?

You are standing in the supplement aisle, or more likely scrolling through tabs at 10pm, trying to work out whether algae oil or fish oil is the better omega-3 choice. The short answer: it depends on what you are optimising for.

If purity, sustainability, and avoiding animal-derived products matter to you, algae oil wins. If you want the highest combined EPA and DHA dose from a single capsule, fish oil is more efficient. Both deliver the same fatty acid types your body needs.

Phytality manufactures algae-based omega-3 supplements. This article is written from that perspective. We have aimed for accuracy and fairness about both options, including where fish oil has a genuine advantage. When we reviewed the production and contamination data side by side, the differences were larger than the marketing from either side suggests.

How Algae Oil and Fish Oil Are Produced

The production gap between these two is wider than most people realise, and it matters for what ends up in your capsule.

Algae Oil: Controlled Cultivation

Algae oil comes from cultivated microalgae, species like Nannochloropsis (rich in EPA) and Schizochytrium (rich in DHA). Producers grow these in controlled environments: glass-tube bioreactors, closed tanks, or open ponds. The quality difference between methods is significant. Open ponds expose algae to wind, rain, and wildlife. Closed-system bioreactors keep the environment sealed, controlling light, nutrients, and CO2 input at every stage.

If you have ever wondered why two algae supplements at the same price point vary so much in purity claims, the cultivation system is usually the reason.

Fish Oil: Industrial Extraction

Fish oil is extracted from the tissue of oily fish: salmon, cod, anchovies, or krill. The standard process involves cooking the fish at high temperatures, then refining, deodorising, and sometimes winterising the oil to remove impurities. The quality of the output depends on where the fish were caught, how contaminated those waters are, and how quickly the fish were processed after harvest.

The practical difference for you: algae oil production can be controlled from start to finish. Fish oil quality depends on variables no manufacturer fully controls.

Omega-3 Fatty Acid Profiles: EPA, DHA, and What You Actually Get

Both algae oil and fish oil contain EPA and DHA, the two omega-3 fatty acids your body actually uses. EPA and DHA contribute to the normal function of the heart at a combined daily intake of 250 mg, according to EFSA-authorised health claims under Commission Regulation (EU) No 432/2012. DHA contributes to the maintenance of normal brain function and normal vision under the same regulation.

No single algae species produces high levels of both EPA and DHA. Nannochloropsis is naturally rich in EPA, while Schizochytrium produces DHA efficiently. Fish, particularly fatty coldwater species, naturally contain both in their tissue. If you are comparing a single fish oil capsule against a single algae oil capsule, fish oil often delivers a higher combined EPA+DHA dose.

The algae workaround is straightforward: you combine two sources. Our ULTANA Phytoplankton delivers EPA from Nannochloropsis, and Clean Omega DHA provides algae-derived DHA from Schizochytrium. Together, they cover both fatty acid types from plant-based sources.

Contaminants and Purity in Algae vs Fish Oil

This is the section that changes most people's minds. When you swallow a fish oil capsule, you are consuming a concentrated extract of whatever was in that fish's tissue, including anything the fish accumulated from its environment.

Mercury, polychlorinated biphenyls (PCBs), and dioxins are the headline contaminants. They are present in ocean fish because of industrial pollution, and they bioaccumulate: larger, longer-lived fish concentrate higher levels. Reputable fish oil manufacturers use molecular distillation to reduce these contaminants, and many achieve very low levels. But "reduced" is not "absent," and the base material always carries some contamination load from the marine food chain.

Algae oil grown in closed cultivation systems does not face this problem. The microalgae never enter the ocean food chain, so there is no bioaccumulation pathway. That said, not all algae supplements are equal on purity. Open-pond cultivation introduces its own contamination risks, and extraction method matters for the finished product.

Environmental Impact of Algae Oil vs Fish Oil

Fish oil production depends on fishing. Overfishing depletes wild populations, disrupts marine ecosystems, and generates bycatch. Fishing vessels burn fuel, and fish processing creates waste. Even well-managed fisheries impose a burden on ocean ecosystems that land-based production does not.

Algae cultivation happens on land. It uses non-potable water, requires no marine harvesting, and generates substantially lower greenhouse gas emissions than fishing operations. We grow our algae inland in sealed glass-tube bioreactors with no interaction with the marine environment. If environmental impact is part of your decision, this is the strongest argument for choosing algae-derived omega-3.

Who Should Choose Algae Oil Over Fish Oil

Choose algae oil if: you are vegan or vegetarian; you are pregnant or breastfeeding and want to minimise contaminant exposure; you get fish burps from fish oil capsules; environmental sustainability is a deciding factor; or you want to avoid animal-derived products entirely.

Fish oil may suit you better if: you want the highest combined EPA+DHA dose from a single capsule with the least complexity; you have found a high-quality, molecularly distilled product you trust; or budget is your primary constraint and you need the cheapest route to a specific omega-3 dose.

Neither option is universally "better." The right choice depends on what you are prioritising, and being honest with yourself about what actually matters to you versus what sounds good on paper.

Algae vs Fish Oil FAQ

Can algae oil replace fish oil for omega-3?

Yes. It provides the same long-chain fatty acid types. You may need two algae-based products (one for eicosapentaenoic acid, one for docosahexaenoic acid) to match the combined profile of a single marine oil capsule. For most people the switch is straightforward. If you take marine oil for a specific medical reason, check with your GP before changing, as dosing may differ.

Is omega-3 from algae absorbed as well as from fish?

The evidence is still developing. Some studies suggest algae-derived long-chain fats are well absorbed, but direct head-to-head comparisons remain limited. Individual factors like what you eat alongside the capsule and your own digestive efficiency also play a role. We would not claim algae-sourced omega-3 is better absorbed, because the data does not support that as a settled conclusion.

Are there any side effects of algae oil?

It is generally well tolerated. The most commonly reported issue is mild digestive discomfort when starting supplementation, which usually settles within a few days. Unlike marine oil, algae-derived capsules do not cause the fishy reflux that puts many people off. If you take blood-thinning medication, consult your GP before starting any omega-3 supplement, as both EPA and DHA can affect clotting at high doses.

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

Methodology and Disclosure

Phytality manufactures algae-based omega-3 supplements and has a commercial interest in this comparison. EFSA-authorised health claims are cited with their regulatory source. Contamination comparisons reflect published data on bioaccumulation in the marine food chain and published testing of commercial fish oil products. The environmental comparison is an editorial assessment of the structural differences between aquaculture and wild fishery supply chains, not a peer-reviewed lifecycle analysis.

Last reviewed: April 2026