Bicolor blenny
Ecsenius bicolor
Dark front and orange rear; may occasionally nip corals. A blenny that uses rocks and holes as lookout points. Other blennies may be chased as competitors.
At a glance
- Scientific name
- Ecsenius bicolor
- Dutch name
- Tweekleurige slijmvis
- Water temperature
- 24–26 °C
- pH
- 8.1–8.3
- Adult length, up to approximately
- 11 cm
- Experience
- Some experience
- Carbonate hardness (KH)
- 8–12 °dKH
- Specific gravity (SG)
- 1.024–1.025
- Starting volume
- 120 L
- Swimming or living zone
- Rocks & refuges
- Flow
- Moderate, with sheltered areas
- With corals
- With caution; read the species notes
This is a documented adult size, not a measured average. SL means body length excluding the tail fin. Sex, origin and cultivated form can affect size.
Care guidance; origin and captive breeding can change requirements. Some ranges are deliberately narrower than natural extremes in the source. Adjust water gradually and keep ammonia and nitrite at zero.
General marine targets also use group-level care guidance. Check the needs of your corals too. SG is not salinity in ppt; follow your instrument’s temperature calibration.
Tank sizes are editorial starting points for adults, not guarantees for a complete stocking plan. Group size, tank height, swimming length and territories may require a larger aquarium.
Origin
Indo-Pacific region
Habitat & setup
Tropical reef with rocks, crevices and open water.
Diet
Ample mature rock growth and targeted supplementary food, including seaweed and suitable complete marine food.
Behaviour & grouping
Prefer one specimen per territory; pairs only when demonstrably compatible.
Living with other animals
Peaceful reef fish of suitable size with separate refuges. Check species-specific aggression and shrimp risks separately.
Possible combinations to investigate further
- Common clownfish
24–26 °C · pH 8.1–8.3
Reproduction
Breeding requires species-specific expertise; do not expect successful reproduction in a community aquarium.
A suitable cover helps prevent escape and jumping. Protect intakes for small animals. Do not use copper-based fish medication with invertebrates.
Sources & image credits
Data compiled on: 2026-09-27. Species sources support identity and care; group sources give general starting points. Practical recommendations are an editorial synthesis.
Photo: Bicolor_blenny_Ecsenius_bicolor.jpg — Brian Gratwicke. CC BY 2.0.