Decorated dragonfish
Eustomias decoratus
The Decorated dragonfish features a slender body with bioluminescent photophores and iridescent, dark brown to black coloration.
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About the Decorated dragonfish
Eustomias decoratus is a deep-sea dragonfish (family Stomiidae) from the western central Atlantic around Bermuda. Like other Eustomias, it is a pelagic predator built for the dark - long body, big mouth, and a chin barbel used in hunting and signaling. This is absolutely not an aquarium species in any normal sense, since its real habitat is open ocean at depth and it will not tolerate typical captive conditions.
Quick Facts
Size
12.9 cm SL
Temperament
Aggressive
Difficulty
Expert
Min Tank Size
0 gallons
Lifespan
unknown
Origin
Western Central Atlantic (Bermuda area)
Diet
Carnivore - pelagic predator on smaller fishes and crustaceans
Care Notes
- Plan around their lifestyle: a dark, quiet, deepwater-style tank with lots of overhangs and caves, zero sudden light changes, and big open water for slow cruising.
- Keep it cold and stable: 39-50 F (4-10 C), salinity 1.025-1.026, pH around 7.8-8.1, and keep nitrate low because they go downhill fast in dirty water.
- High oxygen is non-negotiable - heavy aeration plus serious filtration, and keep surface agitation strong without blasting them with direct flow.
- Feeding is the whole game: start with live marine prey (small shrimp, ghost/glass shrimp acclimated to salt, or small fish) and slowly transition to thawed silversides, krill, or large mysis on feeding tongs right in front of the mouth.
- Feed at night or in near-dark; they key on movement, so wiggle the food and be patient - missed strikes and food rot are your enemy, so siphon leftovers immediately.
- Tankmates: basically none, unless it's a much larger, non-competitive deepwater predator that won't bully it; anything that fits in its mouth becomes food, and fast feeders will starve it out.
- Watch for barotrauma and shipping damage - these deep-sea fish hate rapid pressure/temp changes, and a fish that can't hold depth or has buoyancy issues usually doesn't recover.
- Breeding in captivity is a long shot: they are open-ocean spawners and larvae are pelagic, so don't buy one expecting a breeding project - focus on keeping it eating consistently first.
Compatibility
Good Tankmates
- Other deepwater predators kept with lots of space and a heavy feeding routine - think similar size or bigger viperfish/other dragonfish types, so nobody fits in anyone's mouth (and you are ready for mouthy, nighttime drama anyway)
- Large, tough, midwater hunters that do not freak out in low light - stuff like adult barracudina or big lanternfish types, only if they are clearly too large to be swallowed
- Big, slow cruising fish that are not finny or bite-sized - like larger deepwater cod/rockfish type builds (thick-bodied, not flashy), again the rule is simple: too big to eat, too boring to chase
- Rugged, larger benthic fish that keep to themselves and can handle a rough neighbor - think bigger eelpout/cusk-eel type fish that stay on the bottom and are not snack-sized
- Hardy scavengers and cleanup inverts that will not get hunted as easily - big serpent stars and larger shrimp that are not tiny (you will still lose small ones, so go larger than you think)
Avoid
- Anything small enough to fit in that oversized mouth - anthias, chromis, small wrasses, small damsels, most "community" marine fish are just expensive live food here
- Nippy or feisty tankmates that will harass it or steal food all night - triggers, large aggressive damsels, or pushy wrasses (you end up with constant stress and feeding chaos)
- Slow, fancy-finned fish or delicate show fish - lionfish, longfin bannerfish, anything that drifts around looking easy to grab (or gets shredded in the commotion at feeding time)
Where they come from
Decorated dragonfish (Eustomias decoratus) are deep-sea stomiids - real deal midwater predators from the dark ocean. Think hundreds to thousands of meters down, cold water, high pressure, and basically no light except bioluminescence. That's why you almost never see them in the hobby, and why keeping one alive is firmly in "expert, specialty build" territory.
If you're picturing a normal marine aquarium with live rock and bright LEDs, this fish is going to have a rough time. They are built for darkness, cold, and calm water, not a typical reef setup.
Setting up their tank
I'll be straight with you: the tank is the easy part compared to sourcing a healthy specimen and getting it to eat. But if you do get one, you want to make the environment as low-stress as possible.
Go with a species tank. Dim lighting, lots of open water, and gentle, laminar-ish flow. Skip rock piles that the fish can slam into at feeding time. These are fragile-bodied fish with a "built for the void" vibe, not for bouncing around a busy aquascape.
- Tank size: bigger is better for stability, but prioritize footprint and open swimming space over tall rock structures
- Lighting: very dim, ideally adjustable; avoid sudden on-off transitions
- Flow: moderate and smooth, not chaotic; avoid blasting them with powerheads
- Filtration: oversized and quiet; you want high oxygen and very stable water with minimal turbulence
- Aquascape: sparse; a couple of dark PVC elbows or low-profile structures is plenty
Temperature is the deal-breaker for most people. Eustomias are deep, cold-water fish. A typical 75-78F reef tank is not a good match. Plan on a chiller and a system designed around cold marine temps.
Keep parameters boring and consistent. Stable salinity matters more than chasing numbers. Also, cover every intake. A curious or startled dragonfish can end up plastered to a strainer in seconds, and their skin and fins do not forgive it.
What to feed them
These are ambush predators that eat fish and large zooplankton in the wild. In captivity, the whole game is getting them onto food you can provide repeatedly, without fouling the water.
If you ever keep one, expect live food at the start. Many deep-sea predators will ignore dead offerings until they're settled, and some never convert. Once they're eating, you can try to transition to frozen by mixing, scenting, and using feeding tools.
- Starter foods: live ghost shrimp, live marine shrimp, small live fish only if you can source disease-free (and even then, be cautious)
- Transition foods: thawed silversides, lancefish, pieces of shrimp or squid, enriched mysis for smaller individuals
- How to feed: long feeding tongs or a feeding stick; keep your hands out and movements slow
- Frequency: small meals more often beat one huge meal; big meals can lead to regurgitation and water quality issues
Feed with the lights low and keep the room calm. I've had deepwater predators refuse food just because someone walked past the tank too fast or the lights were ramped up.
Do not use random feeder fish. Parasites and bacteria are common, and a dragonfish that stops eating is hard to bring back.
How they behave and who they get along with
They are sit-and-wait hunters and they spook easily. Expect long periods of stillness, then sudden strikes. If you're expecting an active display fish, you'll be disappointed. If you're into weird, subtle behavior, you'll be glued to the glass.
Tankmates are mostly a bad idea. Anything small enough will be treated as food. Anything large and pushy will stress them out or outcompete them. Even "peaceful" community fish can be a problem just from constant motion and feeding frenzy vibes.
- Best setup: alone
- Avoid: aggressive fish, fast feeders, bright reef fish, and anything nippy
- Also avoid: strong stinging corals and anemones if you were thinking reef (they will blunder into them)
Deep-sea stomiids use bioluminescence for hunting and signaling. In a home tank you won't recreate the real light environment, but keeping things dim and predictable seems to reduce stress behaviors.
Breeding tips
Realistically, breeding Decorated dragonfish in a home aquarium is not on the table. Their natural breeding and early life stages happen in open ocean conditions we can't mimic well, and just keeping an adult stable is already a major project.
If you ever hear a claim of captive breeding here, I'd treat it as "needs strong proof." The best you can do is keep detailed notes: temps, photoperiod, feeding, and any seasonal behavior changes. Those logs are actually useful to the tiny number of people attempting deep-sea husbandry.
Common problems to watch for
Most losses happen in the first stretch: shipping trauma, refusal to feed, or a slow slide from stress. These fish are not forgiving, and they don't bounce back like hardier marine predators.
- Not eating: the big one; often tied to bright light, too much flow, or too much activity around the tank
- Mouth and jaw damage: can happen from striking glass, rock, or hard feeding tools
- Intake injuries: uncovered overflows and powerhead intakes are a common, ugly end
- Rapid breathing: can mean low oxygen, temp issues, or ammonia - check the basics immediately
- Wasting away: looks like "they eat sometimes" but still get thinner; can be internal parasites or just not enough calories
If water quality slips, you often don't get a second chance. Keep ammonia and nitrite at zero, keep nitrate low, and do small, frequent water changes instead of big swings.
Quarantine is tricky with a fish like this, but skipping it is how people import problems into a cold system that's expensive and slow to stabilize. If you can, run a dim, chilled QT with mature biofiltration and minimal handling.
Similar Species
Other marine aggressive species you might be interested in.
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This is a New Zealand stargazer that lives half-buried in sand or mud with its eyes pointed up, waiting to rocket upward and nail passing prey. It has those neat dark saddle-bands across the back (especially as a juvenile), and like other stargazers it is venomous with spines near the gill cover/pectoral area - definitely a look-dont-touch fish.
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Bathophilus kingi is a tiny deep-sea dragonfish that lives way down in the dark, with that classic stomiid vibe: slim body, big teeth, and built for hunting in open water. It is not an aquarium fish in any realistic sense - it is a bathypelagic marine species that comes from extreme depths where pressure and conditions are totally different from home tanks.
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Rogadius serratus is a sneaky little flathead that basically lives glued to the bottom, blending into sand and rubble like a living leaf-litter camouflage job. It is the kind of fish that does almost nothing until food shows up, then it strikes fast. Super cool look up close, but it is absolutely not a community tank fish.
More to Explore
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Aleutian skate
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This is a big, cold-water deep-slope skate from the North Pacific that cruises muddy bottoms and eats chunky benthic prey like crabs and shrimp. The really cool bit is its egg-laying skate life - it does distinct pairing (the classic skate "embrace") and drops those tough egg cases on the seafloor. Not an aquarium fish at all unless you're basically running a public-aquarium-style chilled system.
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Brama brama is the Atlantic pomfret (aka Ray's bream) - a deep-bodied, open-ocean pelagic fish that cruises around in small schools and follows water temps. It is a legit big, wild marine species (not an aquarium fish) that eats other small sea critters like fish and squid, and it ranges across a huge chunk of the Atlantic plus parts of the Indian and South Pacific.
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