Bicolour Blenny

Aquarium Requirements

Minimum Tank Size: 75 litres (20 US gallons)

Temperature: 24–28 °C (75–82 °F)

pH: 8.1–8.4

Specific Gravity (Salinity): 1.020–1.025

Alkalinity: 8–12 dKH

Ammonia & Nitrite: 0 ppm

Nitrate:< 10 ppm

Aquascape:
Provide abundant live rock to support natural algae growth and offer multiple hiding places and perches. The Bicolour Blenny favours rocky areas with plenty of holes and ledges for shelter. Moderate water flow and stable conditions are important for long-term health. A mature tank with healthy microalgae populations is ideal.

Diet and Feeding

The Bicolour Blenny is primarily herbivorous, grazing on benthic and film algae in the wild. In captivity, it readily adapts to prepared foods, but its diet should remain rich in plant-based materials to prevent malnutrition and potential coral-nipping behaviour.

Recommended Foods:

• Algae- and spirulina-based pellets or flakes

• Frozen herbivore blends and finely chopped mysis shrimp (as occasional supplements)

• Dried seaweed (nori) or macroalgae sheets attached with a clip

• Fresh vegetable matter (e.g. blanched spinach or zucchini, sparingly)

Feed 2–3 times daily in small portions. Ensure ongoing access to natural algae or suitable replacements.

Temperament and Compatibility

The Bicolour Blenny is generally peaceful but can become territorial toward other blennies or similarly shaped fish, especially in smaller aquariums. It coexists well with most non-aggressive community and reef species.

Suitable Tankmates:

• Clownfish, gobies, firefish, cardinalfish, and small wrasses

• Peaceful invertebrates and corals

Avoid:

• Aggressive or territorial species such as dottybacks, large wrasses, and hawkfish

• Other algae-grazing blennies unless housed in a large, well-structured system with multiple territories

Reef Compatibility

✅ Reef Safe (with caution)

The Bicolour Blenny is reef safe under normal conditions and does not typically harm corals or invertebrates. However, if underfed or lacking natural algae, some individuals may nip at soft corals, polyps, or clam mantles while grazing. Providing consistent access to plant-based foods prevents this behaviour.

Additional Information

Maximum Size: 10–11 cm (4–4.5 inches)

Lifespan: 4–6 years in captivity

Difficulty Level: Easy to Moderate (hardy but requires herbivorous diet)

Natural Behaviour: Perching, grazing, inquisitive, territorial around chosen rockwork

Origin: Indo-Pacific – Red Sea to western Pacific Ocean

Colouration: Distinct dark anterior half with bright orange to yellow posterior; some regional and individual colour variations occur

Summary

The Bicolour Blenny (Ecsenius bicolor) is a hardy, personable, and visually striking reef fish prized for its vivid two-tone coloration and amusing behaviour. As both a functional algae grazer and a characterful aquarium inhabitant, it thrives in tanks with abundant live rock, stable water conditions, and a predominantly herbivorous diet. With proper care, the Bicolour Blenny adds both colour and personality to any reef environment.