Chaetoceros gracilis – Premium Marine Diatom Phytoplankton

Scientific Classification

Kingdom: Chromista | Phylum: Bacillariophyta | Class: Coscinodiscophyceae | Order: Chaetocerotales | Family: Chaetocerotaceae | Genus: Chaetoceros | Species: C. gracilis

Chaetoceros gracilis Complete Profile

Chaetoceros gracilis is a small, fast‑growing marine diatom measuring 3–6 micrometers in diameter. It forms single cells or short chains and is characterized by its thin silica frustule and delicate setae (spines). This species is widely used in aquaculture due to its high EPA content, rapid growth rate, and excellent digestibility for copepods, bivalves, and larval fish.

Exceptional Nutritional Composition

Protein Content: 35–45% dry weight Lipid Content: 10–18% dry weight with strong omega‑3 enrichment:

• EPA Content: 20–35% of total fatty acids

• DHA Content: Trace to none (typical for diatoms)

• Carotenoids: High fucoxanthin concentration

• Silica Content: Thin frustule, highly digestible compared to larger diatoms

Digestibility: Excellent — the small cell size and thin silica walls make C. gracilis one of the most digestible diatoms for nauplii and filter feeders.

Why Chaetoceros gracilis Excels

High EPA Production: EPA levels in C. gracilis are among the highest of any cultured phytoplankton species, supporting membrane development, stress tolerance, and reproductive output in zooplankton.

Perfect Cell Size for Larvae: At 3–6 µm, C. gracilis is ideal for:

• Copepod nauplii

• Oyster, clam, and mussel larvae

• Early‑stage fish larvae requiring small, digestible particles

Rapid Growth Rate: This species doubles quickly under standard culture conditions, making it a cost‑effective and reliable base feed in hatcheries.

High Fucoxanthin Content: Fucoxanthin supports antioxidant activity and pigmentation in marine organisms.

Marine Copepod Production

Optimal Copepod Nutrition: Calanoid copepods (e.g., Acartia tonsa, Parvocalanus crassirostris, Pseudodiaptomus pelagicus) show excellent growth and survival when fed C. gracilis. The high EPA content accelerates nauplii development and improves adult vitality.

Enhanced Reproductive Output: Copepods fed C. gracilis produce:

• Higher egg clutch sizes

• Faster nauplii development

• Improved survival across multiple generations

Synergy With Other Species: Often paired with Tisochrysis lutea or Rhodomonas species for balanced EPA/DHA enrichment.

Culture Methodology

Optimal Cultivation Parameters:

• Salinity: 25–35 ppt, optimal 28–32 ppt

• Temperature: 18–26°C, optimal 20–24°C (68–75°F)

• pH: 7.8–8.4

• Light: 100–200 µmol photons m⁻² s⁻¹

• Photoperiod: 16:8 or 24:0 light:dark

• Growth Rate: Doubling time 12–24 hours under ideal conditions

Culture Challenges:

• Requires silica supplementation (standard f/2‑Si media)

• Sensitive to shear stress in high‑flow aeration

• Can form chains under stress, slightly increasing cell size

Reef Aquarium Applications

Filter‑Feeding Invertebrates: Chaetoceros gracilis is highly effective for:

• Feather dusters

• Sponges

• Bivalves

• Tunicates

• Non‑photosynthetic corals

The small cell size ensures high capture efficiency and digestion.

Copepod Population Support: Regular additions maintain dense copepod populations, improving natural microfauna diversity and providing continuous live food for reef fish.

Coral Supplementation: While not as pigment‑rich as red species, the high EPA content supports tissue repair, polyp extension, and overall metabolic health.