Green-peritoneum snailfish
Paraliparis entochloris
Also known as: Snailfish, Seasnail
Paraliparis entochloris is a deepwater snailfish from the northwest Pacific, and the name is basically calling out its weird party trick: it has a green peritoneum (the lining around the organs) that can show through the body wall. This is not an aquarium fish at all - it is a cold, deep, bottom-associated species that is mostly known from scientific collections rather than the hobby.
The Green-peritoneum snailfish features a slender body adorned with translucent, pale green skin and a distinctive, elongated dorsal fin.
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Quick Facts
Size
8.7 cm SL
Temperament
Peaceful
Difficulty
Expert
Min Tank Size
180 gallons
Lifespan
unknown
Origin
Northwest Pacific
Diet
Carnivore - likely small benthic invertebrates (deepwater micro-predator)
Water Parameters
0-6°C
7.8-8.4
8-12 dGH
Need a heater for this species?
This species needs 0-6°C in a 180 gallon tank. Use our heater calculator to find the right wattage.
Calculate heater sizeCare Notes
- Plan the tank like a chiller build, not a reef - these are deepwater snailfish and they crash fast if you try to run them warm. Keep it cold and steady (think 34-41F / 1-5C) with high O2 and strong surface agitation.
- Low light, lots of overhangs, and soft bottoms help - they like to wedge under rock and rest, and they bruise easily on sharp rubble. Use smooth rockwork and give them tight caves they can actually fit into.
- Keep salinity around natural seawater (1.025-1.026) and do not let pH swing; stability beats chasing numbers. Ammonia and nitrite need to be dead zero, because they do not handle any burn at all.
- Feed small meaty stuff they can suck down: mysis, chopped krill, enriched brine, and tiny bits of clam or squid. Target feed with a pipette near their hide so faster fish do not steal everything.
- Avoid aggressive or hyper tankmates - even 'peaceful' wrasses and anthias will outcompete and stress them. If you want company, pick slow coldwater species and inverts that will not pick at a resting fish.
- Watch for barotrauma and decompression damage on new arrivals (floaty, can not stay down, weird posture) - that is a common reason they fail early. Also keep an eye on skin scrapes and fin rot from rough décor or warm temps.
- Breeding in home tanks is basically a long-shot; if you ever see eggs, they will likely be laid in a protected crevice and the adults may guard or at least hang nearby. If that happens, leave the area alone and keep flow gentle so you do not blast the clutch.
Compatibility
Good Tankmates
- Small, calm deepwater-type fishes like other Paraliparis snailfish or similar little slope sculpins - basically anything that just hovers or perches and minds its own business
- Non-nippy, coldwater/temperate goby-type fish (tiny sand/perch gobies, quiet benthic micro-predators) that will not hassle a slow, soft-bodied fish
- Gentle inverts like small shrimp, amphipod and copepod cultures, and non-predatory snails - they help keep the tank active without stressing the snailfish
- Filter feeders and peaceful cleanup crew like small brittle stars, mini feather dusters, and detritivore worms - good neighbors as long as you are not trying to keep a prized pod population untouched
- Other super chill, coldwater community picks like tiny pricklebacks or very small gunnels that are not bitey and are fed well (think 'perch and hide' behavior, not hunters)
- Small, non-stinging soft coral and macroalgae setups - not a 'tank mate' fish, but in practice these tanks keep lighting and flow mellow, which suits them
Avoid
- Anything aggressive or pushy like dottybacks, damsels, or most wrasses - they will pester it and outcompete it at feeding time, and a snailfish usually loses that battle
- Predators that see it as a snack - groupers, larger scorpionfish, anglers/frogfish, big hawkfish - if it fits in the mouth, it is on the menu
- Nippy fin-pickers and 'curious biters' like some triggers and larger puffers - even if they do not eat it, they will chew on a slow, squishy fish
- Big, bulldozer bottom fish like large crabs, big lobsters, or aggressive urchins - they will crowd it off perches and can injure it during night roaming
Where they come from
Paraliparis entochloris is a deep-sea snailfish. Think cold, dark water, high pressure, and a life spent hovering close to the bottom picking at tiny prey. The name comes from a greenish tint in the belly lining (the "green peritoneum"), which is one of those weird deep-water quirks you only see in animals that live far from sunlight.
This is an expert-only animal for a reason: deep-sea species do not handle warm temps, bright lights, sloppy water, or shipping stress the way normal marine fish do.
Setting up their tank
If you are picturing a typical reef tank, flip that idea on its head. Snailfish like this want cold, stable water, low light, and a calm tank where nothing is trying to outcompete or harass them. Stability beats fancy.
- Temperature: cold. You are realistically in chiller territory, and you want it rock steady.
- Lighting: dim. They do better with subdued light and lots of shadowed areas.
- Flow: gentle to moderate, but not blasting the bottom. They are hover-and-perch fish.
- Aquascape: smooth rock, caves, and overhangs. Skip sharp rubble that can scrape a soft-bodied fish.
- Bottom: fine sand or bare bottom. If you use sand, keep it clean and not too coarse.
- Filtration: oversized biofiltration and serious oxygenation. Cold water holds oxygen well, but you still want strong gas exchange.
Build the tank around easy feeding and easy cleaning. A lot of deep-water fish fail in home systems because food gets lost in rockwork and the keeper chases parameters instead of controlling waste.
Cover intakes and any gaps. Snailfish are not fast swimmers, and a tired or stressed fish can get pinned to a strong intake. Also, keep the tank quiet: no big temp swings from nearby windows, no heaters cycling on and off (you should not be heating this tank anyway), and no wild salinity swings from sloppy top-off.
Do not attempt this without a reliable chiller and a backup plan (controller alarms, spare pump, power contingency). A few hours of the wrong temperature can be the end of the fish.
What to feed them
They are small-predator fish: meaty, bite-sized foods, offered where they can find it without competing with faster fish. In my experience, the biggest hurdle is not "will it eat" but "will it keep eating after shipping stress." You want a fish that takes food early and regularly.
- Start foods: enriched mysis, chopped shrimp, small pieces of clam, and other soft marine meats.
- Live options (useful for getting them started): live mysids or other small crustaceans if you can source them cleanly.
- Avoid: big chunky foods, oily freshwater feeders, and anything that fouls the tank fast.
Target feeding helps a lot. Use a feeding tube or long tongs and place the food right in front of the fish near its favorite perch. I like smaller meals more often at first, then settle into a steady routine once it is eating confidently.
Watch the fish, not just the feeding response. A snailfish that eats once and then disappears for days is a red flag. You want consistent interest and a slow, steady body profile (no pinched belly).
How they behave and who they get along with
These are calm, low-energy fish. They perch, hover, and make short moves rather than cruising the tank. They are not built for brawling or racing to food, so "peaceful" tankmates still might be a problem if they are pushy at mealtime.
- Best setup: species-only or a very quiet coldwater community with similarly slow feeders.
- Avoid: aggressive fish, fast fish that mob food, and anything that nips fins or picks at soft-bodied animals.
- Inverts: even some "reef safe" clean-up critters can be a nuisance if they steal food right off the fish's nose.
A lot of compatibility issues show up as feeding problems first. If the snailfish starts eating less after you add something new, assume stress or competition until proven otherwise.
Breeding tips
Realistically, breeding Paraliparis in home aquariums is a long-shot. Deep-sea fish often have triggers tied to seasonal cues, depth-related conditions, and very specific food availability. That said, if you ever did want to try, the best starting point is keeping them stable for a long time and observing courtship behavior (pairing, staying close, guarding a spot).
- Keep notes: temp, photoperiod, feeding schedule, and any behavior changes over time.
- Provide egg-laying surfaces: sheltered caves and smooth rock faces.
- If you ever see eggs: keep flow gentle around them, keep the tank dim, and resist the urge to mess with them.
Do not chase breeding by changing a bunch of variables at once. With deep-water fish, sudden changes usually backfire.
Common problems to watch for
Most losses come from stress stacking: shipping stress, wrong temperature, bright light, too much flow, then missed meals, then water quality issues. You have to break that chain early.
- Temperature creep: chiller failure or room heat slowly pushing the tank warmer than you think.
- Refusing food: often tied to stress, competition, or the food being too large or too "dry" (not enticing).
- Damage from intakes or rockwork: soft-bodied fish can get scraped or pinned easily.
- Oxygen issues at night: less common in coldwater, but it can happen in tanks with heavy bacterial load or low surface agitation.
- Rapid decline after "looking fine": deep-sea fish can crash fast once they stop eating or get hit with a parameter swing.
If you see a behavior change (hiding more, breathing harder, not perching normally), test immediately and then simplify: dim the lights, reduce disturbance, and offer small target-fed meals while you stabilize the tank.
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