The Bicolor Blenny is a hardy, comical fish, dusky blue at the front and orange at the back, with expressive eyes and a habit of perching and peeking from rocks.
Its personality and toughness make it a popular beginner marine.
It is reef-safe and helps graze film algae, though it needs supplemental feeding once natural algae thins.
Easy to keep and full of character, it suits new and experienced reef keepers alike.
Housing
House in a reef tank of at least 110L (30 gallons) with plenty of live rock providing algae, perches, and a hole or crevice it can claim as a home base.
A mature tank with algae film suits it well.
Maintain temperature 24-27C (75-81F), salinity 1.024-1.026, pH 8.1-8.4, and ammonia and nitrite at zero.
A secure rock retreat gives this perching fish confidence and frequent visibility.
Diet
An algae-leaning omnivore that grazes film algae and diatoms but also takes meaty foods.
Offer dried nori, spirulina flakes, algae pellets, and frozen mysis and brine shrimp one to two times daily.
A varied diet weighted toward vegetable matter keeps it healthy and reduces any temptation to nip corals.
Supplement well once natural tank algae is grazed down to prevent a hollow belly.
Health
Hardy and disease-resistant relative to many marine fish, though quarantine and stable water are still sensible.
Most losses come from starvation in algae-poor tanks or from jumping rather than from illness.
Watch the belly profile and appetite; a pinched stomach signals the need for more food.
Provide a secure lid, as bicolor blennies are capable jumpers given any open gap.
Temperament
Generally peaceful but territorial toward other blennies and sometimes similar small fish, occasionally nipping at tankmates that invade its space.
Keep one per tank unless you have a bonded pair.
It is reef-safe with corals and invertebrates, though the rare individual may nip coral polyps if underfed.
Mostly it is an entertaining, characterful fish that perches openly and interacts with its keeper.
A good fit for
Beginners wanting a hardy, characterful fish
Reef tanks with film algae to graze
Keepers who will supplement with nori
Peaceful community reef systems
Common mistakes to avoid
Starves in tanks lacking enough algae
Known jumper; needs a secure lid
Two blennies together usually fight
Rare underfed individuals may nip corals
Is your enclosure big enough?
Minimum volume110 litres (29 US gallons)
CompanyMust be housed alone. One per tank unless a bonded pair
In a reef, stability matters more than any single target number. A parameter moving fast does more damage than a parameter sitting slightly off.
Go now
Any detectable ammonia or nitriteWater change now with matched, mixed and aerated saltwater. Stop feeding. Directly toxic, and a marine system has less margin than a freshwater one.
Now
Temperature or salinity has moved sharplyCorrect slowly, over hours, not minutes. Check the heater and the top-off. The speed of the change does the damage. Correcting fast repeats the injury in the other direction.
Now
Rapid gilling, or a fish hanging in the flow breathing hardIncrease aeration and check temperature and salinity. Warm water holds less oxygen, and a heater failure shows up here first.
Now
Today
White spots, or a fine dusting like icing sugarIdentify which parasite before treating. Most reef tanks cannot be treated in place. The two common parasites look similar and need different handling; velvet can kill a tank in days.
Today
Corals closed for more than a day, or receding tissueTest alkalinity first, and compare it against the last reading rather than a target. Unstable alkalinity is the most commonly cited coral killer, and a swing shows up in the trend, never in a single point.
Today
A new fish added without quarantine now looks unwellRemove it to a separate system today if you can. Nearly every wipeout in a reef tank traces back to a skipped quarantine.
Today
Quarantine every new animal, including corals and inverts. It is the single practice that separates a reef that lasts from a reef that restarts.
This is general guidance for a healthy adult, not a diagnosis. An exotics vet who knows your animal always overrides it — and the time to find one is before you need one.
What it really costs
Setup, monthly, first year and across a whole life, itemised and with the electricity worked out from the actual wattage. Published figures for the same animal disagree by a factor of four, so the calculator shows ranges rather than picking one.
Beginner
Beginner
Beginner
Beginner
Beginner
Beginner