Best Omega-3 for Dogs: Fish Oil vs Plant-Based Oils Explained

Marine & Plant Omega Sources for Dogs

Fish oil is often unfairly scrutinised within the nutrition space for supposedly being “rancid” or oxidised. However, this concern is largely overstated and not reflective of the true quality of regulated products available in Australia and New Zealand.

A 2016 study commissioned by the Therapeutic Goods Administration (TGA) tested a wide range of Australian and New Zealand fish oil products. It found that all met their labelled omega-3 content claims, and none were rancid or oxidised beyond acceptable limits.

Read the study here:
https://pmc.ncbi.nlm.nih.gov/articles/PMC4728664/

When sourced from reputable suppliers and stored correctly, fish oil remains one of the most stable, effective, and scientifically supported sources of omega-3 fatty acids.

A Complete Comparison of Omega Oil Sources

This guide compares the most common marine and plant-based omega oil sources for dogs, including:

• Fish Oil
• Krill Oil
• Cod Liver Oil
• Calamari Oil
• Marine Phytoplankton
• Algae Oil
• Flaxseed Oil

We’ll break down their omega-3 content, vitamin profile, bioavailability, and best use cases.

Fish Oil

Pros

• Excellent, proven source of omega-3s for dogs (EPA + DHA)
• Supports joint health, skin and coat condition, cognition, and inflammation balance
• High concentrations of EPA and DHA per serving

Cons

• Can oxidise easily if not stabilised or refrigerated
• Lower-quality sources may contain heavy metals
• Sustainability varies depending on fish source

Note:
Best used as a reliable, concentrated omega-3 source. Choose oils from small, cold-water fish like anchovy and sardine, and always opt for high-quality, tested products. Smaller bottles are ideal so they are used quickly and stay fresh.

This is my go to brand for Fish oil. 

Krill Oil

Pros

• Omega-3s bound to phospholipids for superior absorption (around 1.5–2× higher)
• Contains natural astaxanthin for antioxidant and anti-inflammatory support
• Low contamination risk due to sourcing from clean Antarctic waters

Cons

• More expensive per mg of EPA and DHA
• Not suitable for dogs with shellfish allergies
• Sustainability can be a concern depending on sourcing

Note:
Ideal for dogs needing high bioavailability and added antioxidant support. A strong all-rounder for joints, brain, and coat health.

This is my go to brand for Krill oil.

Cod Liver Oil

Pros

• Contains EPA, DHA, and natural vitamins A and D
• Supports immune health, joint function, and skin barrier integrity
• Particularly valuable for supporting vitamin D intake
• Highly bioavailable when given with meals
• Supports inflammation balance

Cons

• Vitamin A and D levels can vary, increasing risk of excess if combined with fortified foods like kibble or other supplements
• Less stable than krill oil (higher oxidation risk)
• Slightly lower EPA/DHA ratio compared to purified fish oils

Note:
Excellent for dogs needing immune, joint, and coat support. Particularly useful in fresh feeding to help meet vitamin D requirements. Best used 2–3 times per week rather than daily.

Calamari Oil

Pros

• Very high in DHA, supporting brain, eye, and neurological health
• Low in contaminants and sustainably sourced (often a byproduct of the human food industry)
• Gentle on digestion and well tolerated
• Ideal for puppies, seniors, and breeding dogs

Cons

• Lower in EPA, so less focused on inflammation support
• More expensive and less widely available

Note:
Best for cognitive and visual support. A great addition for dogs needing higher DHA intake.

Marine Phytoplankton

Pros

• Contains EPA, chlorophyll, amino acids, minerals, and antioxidants
• Sustainably grown without depleting marine ecosystems
• Supports detoxification, cellular repair, and antioxidant function

Cons

• Low overall omega-3 concentration and lacks DHA
• Overuse may lead to loose stools due to chlorophyll and mineral content
• Quality varies significantly depending on production methods

Note:
Best used as a marine superfood alongside other oils, not as a primary omega-3 source. It is often marketed as a superior omega-3 option, but it does not provide meaningful levels of EPA and DHA.

Flaxseed Oil (Plant-Based)

Pros

• Plant-based and sustainable
• Provides ALA (a precursor to omega-3)
• May support coat condition and mild inflammation
• Suitable for dogs with seafood allergies

Cons

• Dogs convert less than 10% of ALA into EPA and almost none into DHA
• Limited benefit for joints, inflammation, or cognitive health
• Oxidises quickly when exposed to air and light

Note:
A useful addition for coat support, but not a replacement for marine omega-3s. Flaxseed oil should not replace marine-based sources.

Algae Oil

Pros

• Rich in DHA (and sometimes EPA depending on strain)
• Free from heavy metals and highly sustainable
• Supports brain, eye, and cognitive health
• Ideal for puppies, pregnant or lactating dogs, and seniors
• Vegan-friendly alternative to marine oils

Cons

• Typically low in EPA unless specifically formulated
• Less effective for inflammation support on its own
• Slightly more expensive
• Some dogs may dislike the smell

Note:
Best used for DHA-focused support. Can be combined with fish or krill oil to create a balanced EPA and DHA profile.

Understanding ALA Conversion (Why Plant Oils Fall Short)

Flaxseed oil contains ALA, a plant-based omega-3 precursor.

Dogs can only convert:

• Around 5–10% into EPA
• Almost none into DHA

This is why marine oils are significantly more effective for:

• Joint mobility
• Inflammation balance
• Brain and cognitive health

Final Recommendation

Marine oils remain the gold standard for canine omega-3 supplementation.

• Fish, krill, and cod liver oil should form the foundation
• Calamari oil is ideal when DHA is the priority
• Algae oil is a strong alternative where marine sources aren’t suitable
• Flaxseed oil can complement but should not replace marine oils

For best results:

• Use a marine-based oil as your base
• Store oils in a cool, dark place or refrigerate
• Choose high-quality, tested products

It’s worth noting that much of the negative commentary around fish oil often comes from brands promoting alternative omega-3 sources.

Many of these products are marketed as “cleaner” or superior. In reality, they often lack meaningful levels of EPA and DHA, which are the omega-3 fatty acids responsible for most of the benefits.

These alternatives can have a place in a balanced diet, but they should not replace marine-derived EPA and DHA.

Please note, all product recommendations are based on personal experience. I’m not affiliated with any brands and do not earn commission from these products.