Midas Blenny
Ecsenius midas
Golden, eel-like swimmer with bold charmBeginner
- Lifespan
- 4-6 years
- Size
- 10-13cm (4-5in)
- Social needs
- One per tank unless a bonded pair
- Time
- Low
- Cost
- Medium
- Diet
- Omnivore, zooplankton and algae
Overview
What is this animal?
- The Midas Blenny is a golden-yellow fish with bright eyes and a graceful, eel-like swimming style unusual among blennies.
- Hardy and personable, it is a good beginner marine fish that often hovers in open water rather than perching.
- Unlike many blennies it is a midwater feeder that associates with the anthias it naturally schools with.
- It can shift colour from gold to bluish depending on mood and surroundings.
Temperament
- Peaceful toward most species but territorial toward other blennies and sometimes similar-shaped fish.
- Keep one per tank unless you obtain a bonded pair, as two unpaired individuals may fight.
- It is bold and outgoing once settled, often hovering in the open and interacting with its keeper.
- Reef-safe with corals and invertebrates, it integrates smoothly into peaceful community systems.
A good fit for
- Beginners wanting a hardy, active fish
- Reef community tanks needing midwater interest
- Keepers wanting an outgoing, visible fish
- Peaceful reefs with corals and inverts
Common mistakes to avoid
- Two unpaired blennies will fight
- Needs a secure rock retreat to settle
- Can jump; a tight-fitting lid helps
- Aggressive tankmates may bully it
Enclosure
Minimum 110 litres (29 US gallons)
Must be housed alone. One per tank unless a bonded pair
- Provide a reef tank of at least 110L (30 gallons) with live rock offering caves and crevices it can dart into and claim.
- It favours a hole or tube as a base from which it watches the tank.
- Maintain temperature 24-27C (75-81F), salinity 1.024-1.026, pH 8.1-8.4, and ammonia and nitrite at zero.
- A secure rockwork retreat makes for a confident, frequently visible fish.
Supplies
Setup
- Tank, stand and sump
- Return pump and powerheads
- Protein skimmer
- Reef lighting
- Rock and sand
- Salt mix, refractometer and test kits
- Quarantine tank
Ongoing
- Dried marine algae (nori) sheets
- Magnetic or suction veg clip
- Spirulina flake and algae pellets
- Frozen mysis shrimp
- Frozen enriched brine shrimp
- Marine flake or small pellet
- Small thawing cup and strainer
Safe substrate: Aragonite sand · Dry or cured live rock · Bare bottom
Care routine
Daily
- Check salinity, temperature and flow
- Feed
- Head-count and look everyone over
- Top up evaporation with fresh water
Weekly
- Offer nori on a clipevery 2 days
- Service the skimmer and filter socksevery 3 days
- Check the belly profile
- Clean the glass
- Test the water
Monthly
- Water changeevery 2 weeks
- Calibrate the refractometer
- Check salt, RO/DI and reagents
Less often
- Deep-clean pumps and powerheadsevery 3 months
- Replace RO/DI filter mediaevery 6 months
Vet: Quarterly belly-profile review — every 3 months
Top resources for more info
Independent creators and organisations we would send a friend to. We have no affiliation with any of them, and nothing here is sponsored. Links checked 2026-09-19.
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Diet
- An omnivore that feeds largely on zooplankton in the water column, supplemented by some algae.
- Offer frozen mysis and brine shrimp, marine flakes and pellets, and algae-based foods one to two times daily.
- It readily accepts prepared foods and is an enthusiastic feeder, making it easy to keep well-nourished.
- A varied diet maintains its golden colour and active behaviour.
Health
- Hardy and adaptable, with fewer disease problems than many marine fish, though quarantine is still wise.
- Stable water and a varied diet keep it healthy and brightly coloured for years.
- Watch for hiding, faded colour, or refusal to eat as early warning signs.
- Most issues arise from poor water quality, aggressive tankmates, or an immature tank rather than inherent fragility.
Is your enclosure big enough?
Is this urgent?
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
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.
Bedding and substrate
In a marine system the rock and the sand are life support, and how you start them decides the first six months.
Safe
With a caveat
Never
This is our general list for saltwater fish. We have not built one specific to Blennies yet.
My kit says 0.25 ppm. Is that dangerous?
A liquid kit measures total ammonia, but only the un-ionised fraction is really toxic, and that fraction is governed by pH and temperature — each whole pH unit multiplies it roughly tenfold. So the same reading can be nearly harmless in one tank and lethal in another; this works out which one you are in.
Compare with other animals
The same axes for every animal, side by side — the way the guides are written makes that a fair comparison rather than two articles.
Blennies, side by side
Same axes, same care guides — the honest way to choose between types.
See all Blennies side by side →
