Reefphyto Spirulina Flake 45g: High-Protein Marine and Tropical Fish Food

You feed your fish well. The routine is consistent, the water quality is good, and nothing is obviously wrong. But there is a gap between fish that are surviving and fish that are genuinely thriving, and it tends to show most clearly in colour. Anthias that should be vivid orange look washed out. Wrasses that are technically healthy never quite develop the depth of colour you see in the tank photographs that first got you into the hobby.

Colour in marine fish is not cosmetic. It is a direct expression of nutritional status. The pigments that produce those deep oranges, rich blues and vivid purples depend on a continuous supply of specific nutrients, particularly the phycocyanin and chlorophyll found in algae, the concentrated amino acids that drive pigment synthesis, and a high-level Vitamin C input that supports the physiological processes behind colour development and immune function. Most flake foods include these nutrients in trace amounts. Spirulina Flake is built around them.

Reefphyto Spirulina Flake is a complete food for marine and tropical fish, formulated with a spirulina and algae-forward composition at 54% crude protein and 12% fat, with Vitamin C at 676mg/kg, the highest in the Reefphyto flake range. Fed two to three times per week alongside your daily staple, it provides the sustained algae-based nutrition that drives visible colour improvement over weeks, alongside long-term immune resilience that keeps fish in condition through the stresses of reef life.

Over four to six weeks of regular feeding, the difference tends to become visible. Colours deepen and hold. Fish maintain condition more consistently through water changes, new additions, and seasonal shifts. The tank has a vitality about it that reflects fish genuinely receiving what they need.

At Reefphyto we have been working with marine fish nutrition for 18+ years, and Darren is here directly if you want to talk through how Spirulina Flake fits into a complete feeding programme for the fish you keep.

There is a version of every reef fish that most keepers never quite see. The version with fully expressed colour, sustained condition, and the kind of visible vitality that makes a tank look genuinely alive rather than merely maintained. Getting there is not about expensive equipment or obsessive water chemistry. It is almost always about nutrition, and specifically, about whether the fish are receiving the algae-based compounds that drive pigmentation and long-term physiological health.

Spirulina Flake is designed for that gap.

What Is Spirulina and Why Does It Matter for Marine Fish?

Spirulina (Arthrospira platensis) is a blue-green microalgae that has been used in aquaculture nutrition for decades, and for good reason. It is exceptionally dense in phycocyanin, the pigment protein responsible for spirulina's characteristic deep blue-green colour and a potent antioxidant that supports immune function in fish. It is also rich in chlorophyll, a broad spectrum of amino acids including the essential ones fish cannot synthesise independently, and concentrated levels of B-vitamins that support metabolic function throughout the body.

In practical terms, fish that receive regular spirulina feeding develop and sustain colour more effectively than those fed on protein-only diets. The pigmentation pathways in reef fish, the ones that produce the vivid oranges in anthias, the metallic blues in damsels, the layered purples in dottybacks, are biochemically dependent on the compounds spirulina provides in abundance.

This is not a supplement effect. It is a foundational nutrition effect. And it accumulates over time.

What Reefphyto Spirulina Flake Contains

Spirulina Flake is formulated with a composition of fish and fish derivatives, vegetable protein extracts, cereals, yeasts, algae, molluscs and crustaceans, derivatives of vegetable origin, oils and fats, and minerals. The algae-forward ingredient order and spirulina inclusion place it clearly in a different nutritional category to the purely marine protein flakes in the range.

At 54% crude protein it is among the highest in the Reefphyto flake range, and at 12% crude fat it provides the energy density that active reef fish need to metabolise and utilise those nutrients effectively. Fibre sits at 1.5% and ash at 6.8%.

The vitamin profile is the strongest in the range for immune support. Vitamin C is included at 676mg/kg, more than three times the level in Marine Flake Premium and more than thirteen times the level in the specialist supplement flakes. Vitamin C at this level plays an active role in collagen synthesis, wound repair, immune response, and stress tolerance. For fish navigating the ongoing low-level stresses of reef tank life, fluctuating parameters, new tankmates, handling during maintenance, this is a meaningful nutritional contribution, not a marginal one. The full B-vitamin complex covers B1, B2, B6 and B12, alongside Vitamins A, D3 and E.

Which Fish Is Spirulina Flake For?

Spirulina Flake is a complete food for tropical and marine fish, and the composition reflects that broader positioning. Unlike the purely marine-protein flakes in the Reefphyto range, Spirulina Flake suits any fish that benefits from algae-based nutrition, which in practice means the majority of reef community fish.

It works particularly well for fish where colour is a keeping priority: anthias, wrasses, dottybacks, chromis, damsels, clownfish, cardinalfish, fairy wrasses, and similar species where full colour expression is both a health indicator and a primary reason people keep them. Tangs, blennies, and other omnivore-leaning species also benefit significantly from the algae content, particularly where their diet is otherwise protein-forward.

For dedicated herbivores such as tangs that need a high plant-matter proportion daily, Reefphyto Vegetable Flake remains the primary plant-based food. Spirulina Flake serves as the algae-nutrition supplement in the rotation fed two to three times per week, delivering concentrated spirulina compounds alongside the broad protein base that Vegetable Flake does not prioritise.

It is also well suited to marine fish keepers who have a tropical tank alongside their reef system. The formulation covers both communities, making it a genuinely versatile addition to a feeding routine that spans multiple tanks.

How to Use Spirulina Flake in a Feeding Rotation

Spirulina Flake is a complete food and can be fed as the sole food for a period, but its greatest value is in rotation with complementary foods. The colour and immune benefits of spirulina accumulate gradually over weeks: consistent regular feeding matters more than high frequency feeding.

A practical approach for a mixed marine community is to use Marine Flake Premium as the daily staple, and rotate Spirulina Flake in two to three times per week either alongside or as a replacement for the daily feed. This provides the consistent spirulina input that drives colour development without displacing the broad daily nutrition Marine Flake Premium delivers.

For reef keepers also using Krill Flake and Vegetable Flake in their rotation, Spirulina Flake completes a four-flake programme that covers the full nutritional range of a mixed community. All four are available together in the Reefphyto Marine Flake Pack.

Feed once or twice daily, offering only what your fish will consume within two minutes. Spirulina Flake is surface-floating.

Frequently Asked Questions

How quickly will I see a colour improvement?

Colour development from spirulina feeding is gradual and cumulative. Most keepers report visible improvement over four to six weeks of consistent two to three times weekly feeding. The change tends to be most obvious in fish that were previously fed a protein-only diet with no algae component. Fish that were already receiving algae-based foods will show a more subtle refinement of colour depth and saturation.

Is Spirulina Flake suitable as a daily food?

It is a complete food, so daily feeding is nutritionally acceptable. In practice, many keepers prefer to rotate it two to three times per week alongside a broader complete food such as Marine Flake Premium, which gives the tank variety and ensures the full nutritional range is covered across the week. Both approaches work.

How does Spirulina Flake differ from Vegetable Flake?

Vegetable Flake is a cereals-led food with 39% protein, specifically designed as the primary daily food for herbivorous and omnivorous species that need a high plant-matter proportion. Spirulina Flake is a much higher protein food at 54%, built around fish and fish derivatives alongside algae and spirulina. It is closer to a complete marine food with concentrated spirulina enrichment than a dedicated herbivore food. The two serve different purposes in a rotation and both have a place in a complete feeding programme.

Does Spirulina Flake contain artificial colourants?

No synthetic colourants are listed in the formulation. The deep green colour of the flake comes from spirulina and algae inclusion in the composition.

Can I use Spirulina Flake in a tropical freshwater tank?

Yes. It is formulated as a complete food for both tropical and marine fish. For reef keepers who also run a tropical tank, it is a practical crossover product that suits both systems.