Chiou's snake eel
Xyrias chioui
Chiou's snake eel features a long, slender body with a smooth, brownish-grey coloration and small, dark spots along its back.
This page includes AI-generated images. Why am I seeing AI images?
About the Chiou's snake eel
Xyrias chioui is a sand-bottom snake eel from off eastern Taiwan, a long, needle-toothed burrower that lives deeper than the usual reef-tank stuff (around 60-70 m). Its whole vibe is "hide in the substrate and ambush," so it is more of a specialty/public-aquarium-type animal than a typical home fish.
Also known as
Quick Facts
Size
81.9 cm
Temperament
Semi-aggressive
Difficulty
Expert
Min Tank Size
300 gallons
Lifespan
10-20 years
Origin
Western Pacific (Taiwan)
Diet
Carnivore - meaty marine foods (fish, shrimp, crustaceans)
Water Parameters
20-26°C
8-8.4
8-12 dGH
Need a heater for this species?
This species needs 20-26°C in a 300 gallon tank. Use our heater calculator to find the right wattage.
Calculate heater sizeCare Notes
- Give it a big, deep sand bed (3-6 in) of fine sand - they bury and cruise at night, and coarse gravel will scrape them up fast.
- Lock the tank down like its a lid test: tight-fitting cover, sealed overflow teeth, and no gaps around plumbing - these eels will find exits you did not know existed.
- Run reef-like numbers but keep them steady: 76-78F, 1.025-1.026 SG, pH 8.1-8.4, ammonia/nitrite 0, nitrate low (I try under 10-20 ppm).
- Feed meaty marine foods with tongs after lights-out: silversides, shrimp, squid, clam, and quality frozen carnivore blends; start with smaller pieces and work up so it does not spit and foul the water.
- Do not keep it with small fish, shrimp, or crabs you want to keep - if it can fit in the mouth, it is food, especially once it figures out your feeding schedule.
- Tankmates should be chunky and calm (bigger wrasses, tangs, larger angels); avoid fin-nippers and aggressive triggers that will harass it when it is half-buried.
- Watch for skin scrapes and mouth damage from rough rockwork and tight caves - leave open sand lanes and keep sharp rock edges away from its burrow zones.
- Breeding in home tanks is basically a non-event; focus on long-term stability and quarantine because they can come in with parasites and do not handle copper-heavy treatments well.
Compatibility
Good Tankmates
- Medium-to-larger, not-too-nippy reef fish that mind their own business - think tangs and rabbitfish (Zebrasoma, Ctenochaetus, Siganus). They cruise the open water and usually ignore an eel that stays tucked in the sand/rocks.
- Chill wrasses that are not tiny snack-sized and not super aggressive - like Halichoeres and fairy wrasses (Cirrhilabrus). They are active, sleep in the rockwork, and generally dont pick on an eel.
- Dwarf angels with attitude but not murdery - flame, coral beauty, potters, etc. (Centropyge). In my experience they posture a bit, then everyone settles in as long as the eel has caves and sand to bury in.
- Hawkfish (like flame hawkfish) if your eel is well-fed and you are not trying to keep tiny shrimp. Hawkfish are perchers and usually dont bother an eel, and they are too chunky to be easy prey.
- Robust bottom-ish fish that can hold their space - bigger blennies and some gobies that arent tiny (like lawnmower blenny, watchman goby). Provide lots of hides so they are not forced to share the same hole.
- Most larger non-predatory reef fish that are bigger than the eels mouth and not bullies - the big rule is: if it can fit in the eels mouth at night, it is on the menu.
Avoid
- Tiny fish and slender sleepers - small gobies, small firefish, small dartfish. Chiouis snake eels are ambushy and do a lot of hunting after lights-out, so little torpedo-shaped fish can just vanish.
- Small crustaceans you actually want to keep - cleaner shrimp, peppermint shrimp, sexy shrimp. Even a well-fed snake eel will eventually decide shrimp are free snacks.
- Pugnacious cave hogs that will constantly mess with it - dottybacks and really territorial damsels. If they keep pecking and charging the eels head, you get stress and skipped meals.
- Big aggressive predators that see eel-shaped things as competition or food - larger groupers, big triggers, and some puffers. They can harass, bite, or outcompete it hard at feeding time.
Where they come from
Chiou's snake eel (Xyrias chioui) is one of those deepwater, rarely-seen ribbon-like eels that pops up in the hobby more as a special import than a regular store fish. They come from the Indo-Pacific region and are associated with deeper reef slopes and sandy zones where they can tuck themselves away. If you buy one, assume it is been through a long chain and show it some patience.
Most of the ones you see for sale are wild-caught and often arrive skinny or beat up. Plan your setup and food ahead of time so you are not scrambling after it is in the tank.
Setting up their tank
Think like an eel that wants two things: a safe burrow and zero ways to escape. These snake eels are long, strong, and suspicious of open water. If they do not feel they can vanish on command, they will pace and look for a lid gap.
I would not keep one in a small tank. Length matters more than height. Give it a footprint it can cruise without constantly bumping glass, and keep the rockwork stable because they will wedge and dig around it.
- Tank size: plan on a large footprint (4 ft tank minimum, bigger is better), because they are long and like to roam at night
- Substrate: fine sand, deep enough for burrowing (2-4 in is a good starting point). Skip sharp crushed coral
- Rockwork: set rocks on the bottom glass or on a sturdy base, then add sand around them so digging does not topple anything
- Hiding: PVC elbows or short lengths of pipe buried under sand work great as a starter burrow
- Flow: moderate. You want good oxygen and clean water, but not a sandstorm
- Filtration: heavy. These are meaty-food predators and the tank gets dirty fast
- Lighting: they do not care. Dim zones help them settle
Escape-proofing is non-negotiable. Cover every opening: overflow teeth, cable cutouts, return gaps, mesh tops that bow. If its head fits, the rest follows.
Do not put them in a brand-new marine tank. They do way better in a mature system with stable salinity and pH, and they crash hard if ammonia or nitrite shows up.
What to feed them
Feeding is the whole game with this species. Most individuals come in not recognizing prepared foods, and some act like they are starving but still refuse anything that smells wrong to them.
Start with foods that make them react: fresh or frozen-thawed marine meaty items. Use long feeding tongs and feed after lights out. Once they learn the routine, they get a lot easier, but the first couple weeks can be slow.
- Best starters: frozen-thawed shrimp, squid strips, scallop, clam, silversides (sparingly), pieces of marine fish flesh
- If it is stubborn: try live blackworms (if available/safe), live ghost shrimp, or fresh clam to kick-start feeding, then transition to frozen-thawed
- Soaking: a little fish/shellfish juice from thawed food can help trigger a strike
- Schedule: small meals 2-3 times per week beats dumping a huge feeding once a week
- Vitamins: occasional marine vitamin soak helps if the eel arrived thin
Use a feeding station. I like a small glass dish on the sand near its burrow. Less food disappears into the substrate, and you can remove leftovers before they rot.
Avoid freshwater feeder fish. They are a nutritional mess long-term and can bring in parasites. Stick to marine-based foods.
How they behave and who they get along with
Chiou's snake eel is mostly a crepuscular/nocturnal ambush predator. Mine spent the day buried with just the head out, then did slow patrols once the room lights went down. They are not out to pick fights, but they are absolutely built to eat anything that fits.
Tankmates are about size and temperament. You want fish that will not harass it and will not fit in its mouth. Also think about competition at feeding time because shy eels lose weight fast if boisterous fish steal everything.
- Good tankmates: larger, calmer reef fish that do not pester (bigger angels, tangs, rabbitfish, some triggers with caution), and sturdy wrasses that are not bitey
- Bad tankmates: small fish, small wrasses, gobies, blennies, ornamental shrimp, crabs you care about, and anything that sleeps on the sand looking edible
- Other eels: possible in a very large system, but watch for food competition and wrestling in tight caves
Do not expect it to be a showpiece that is out all day. If you want something constantly visible, this will frustrate you. If you like interesting nocturnal behavior, it is a cool one.
Breeding tips
I have never seen confirmed captive breeding of Xyrias chioui in home aquariums, and eels in general have complicated larval stages (leptocephalus larvae) that drift in the plankton. Realistically, you are not going to breed this species in a typical reef setup.
If you keep a single specimen healthy for years, honestly that is the win. The closest thing to a breeding-related tip I can give is: keep stress low, feed varied marine foods, and keep water quality steady so it has the reserves to handle normal seasonal changes in appetite.
Common problems to watch for
Most issues are either shipping damage, starvation from refusing food, or injuries from squeezing into places it should not. They are tougher than they look once settled, but the first month is where people lose them.
- Refusing food: very common at first. Try different textures (thin strips vs chunks), feed after dark, and reduce competition at feeding time
- Weight loss: watch the girth behind the head. A hollow look means you need to change the feeding plan fast
- Escape attempts: repeated nose-rubbing, pacing the glass, and exploring the rim usually means it does not feel secure or found a drafty lid gap
- Scrapes and mouth damage: from rockwork gaps, rough substrate, or pushing at covers
- Parasites (flukes, etc.): wild-caught risk. Heavy breathing, flashing, excess mucus can be signs
- Water quality swings: sensitive to ammonia/nitrite and does not appreciate big salinity changes
Be careful with medications, especially anything copper-based. Eels can react badly. If you have to treat, do it in a separate hospital tank and research the exact product first.
If it is not eating, dim the tank, add an easy burrow (buried PVC works), and feed with tongs right at the entrance. Once it takes a few meals in a row, the whole experience gets a lot less stressful.
Similar Species
Other marine semi-aggressive species you might be interested in.
Barlip reef-eel
Uropterygius kamar
Uropterygius kamar is a smaller moray (a reef-eel) that spends its time tucked into rockwork and coral rubble, poking its head out when it smells food. FishBase notes it comes in two color morphs and lives on reef-associated rubble areas, so in a tank it really appreciates lots of tight caves and crevices. Like most morays its whole vibe is secretive ambush predator, not open-water swimmer.
Barred snake eel
Quassiremus polyclitellum
This is a temperate, bottom-hugging snake eel from New Zealand that lives out on rocky ground in moderately deep water. Its "snake eel" body plan means it is built for slipping through cracks and tight spots, not cruising the water column like most fish. It is absolutely not an aquarium trade species - think "wild marine eel" more than "pet fish."
Bellfish
Johnius fuscolineatus
Johnius fuscolineatus is a small-ish inshore croaker from the western Indian Ocean that hangs around shallow coastal areas and estuaries. Like other croakers/drums (Sciaenidae), it is more of a "saltwater shoreline" fish than a typical home-aquarium species, and it is usually encountered as a wild-caught food/bycatch fish rather than a trade staple.
Bertelsen's duckbill conger
Gavialiceps bertelseni
Deepwater marine conger eel from off western/southwestern Madagascar (western Indian Ocean), reported from roughly 670–1200 m depth; maximum length about 84 cm TL (reported for males). Not a typical aquarium species due to deepwater habitat.
Black verilus
Verilus sordidus
Verilus sordidus (the black verilus) is a deep-reef Caribbean ocean bass with a big eye and a seriously toothy mouth for its size. It is not really an aquarium fish - it is a deeper-water marine species that shows up around rocky bottoms and is rarely seen in the trade.
Blackspotted snake eel
Quassiremus ascensionis
This is a sand-burying snake eel from the tropical Atlantic that likes to sit with just its head poking out, waiting for food. It gets pretty big (around 70 cm) and needs a real marine setup with a deep, soft sand bed and a tight lid because eels are escape artists.
More to Explore
Discover more marine species.
Abe's eelpout
Japonolycodes abei
Japonolycodes abei is a temperate, deepwater demersal eelpout (family Zoarcidae) endemic to Japan (Kumano-nada Sea reported; other sources also report Sagami Bay and Tosa Bay). It is the only species in the genus Japonolycodes and occurs roughly 40–300 m depth, making it an uncommon/atypical aquarium species.
Banggai Cardinalfish
Pterapogon kauderni
Banggai cardinals just sort of hover like little underwater satellites, and the bold black bars with those long, polka-dotted fins look unreal under reef lighting. They're super chill most of the time, but once a pair forms you'll see real "fish drama," and the male will even mouthbrood the babies like a champ.
Blackbreast cardinalfish
Xeniamia atrithorax
This is a tiny deepwater cardinalfish that was only described in 2016, and it stays around 3 cm long max. The cool calling-card is the dark "blackbreast" patch on the chest area and the fact that the males mouthbrood eggs like other cardinalfish, even though it comes from way deeper water than the usual reef tank cardinals.
Blackfin slatey
Diagramma melanacrum
This is a big Indo-West Pacific sweetlips/grunt that cruises reefs and hangs in caves, and it gets that cool yellow-and-silver look sprinkled with dark spots plus the really obvious black on the lower tail and the pelvic/anal fins. Juveniles show up in murkier estuary and silty reef areas, then the adults shift deeper and often sit in small groups until they go hunting at night. In aquariums its size is the whole story - it is a public-aquarium kind of fish once grown.
Blackspot razorfish
Iniistius dea
This is one of the coolest "knife-bodied" wrasses - it hangs over open sand and, when it gets spooked or wants to sleep, it literally torpedoes straight into the sand. Give it a deep, fine sand bed and it will act totally different (and way more natural) than a typical rock-hugging reef wrasse. Adults are usually shy and cruisy with tankmates, but they are not forgiving about rough handling or sketchy setups.
Blue Green Chromis (Green Chromis)
Chromis viridis
Blue Green Chromis are those shimmery little green-blue darts you'll see zipping around the top of a reef tank, always looking like they're catching the light just right. They're super fun in a group because they hover and cruise together, but they've got a bit of a "pecking order" thing going on if the tank's tight or the group's too small.
Looking for other species?