Southwell's pipefish
Siokunichthys southwelli
Southwell's pipefish features a slender, elongated body with a brownish coloration and distinctive, small dorsal fins positioned far back.
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About the Southwell's pipefish
A tiny tropical marine pipefish from Sri Lanka and the Philippines. Like many syngnathids, it is a slow, deliberate feeder that may require abundant small live foods and low-competition tankmates in captivity.
Also known as
Quick Facts
Size
4.3 cm
Temperament
Peaceful
Difficulty
Expert
Min Tank Size
30 gallons
Lifespan
2-5 years
Origin
Western Indian Ocean: Sri Lanka; Western Central Pacific: Philippines
Diet
Carnivore/micro-predator - live copepods, amphipods, enriched baby brine shrimp; sometimes frozen mysis if trained
Water Parameters
24-28°C
8.1-8.4
8-12 dGH
Need a heater for this species?
This species needs 24-28°C in a 30 gallon tank. Use our heater calculator to find the right wattage.
Calculate heater sizeCare Notes
- Give them a tall, calm tank with lots of fine branching hitching spots (gorgonians, macro like Caulerpa, fake coral trees) and low-to-medium flow - they spend most of their day clinging and snicking at tiny prey.
- Keep salinity stable and avoid rapid swings; provide a mature system and observe closely to ensure consistent feeding and body condition.
- They are slow, picky micro-predators - plan on multiple small feedings of live foods like enriched baby brine, copepods, and tiny mysis; most won"t compete for frozen unless you wean patiently with a feeding station.
- Set up a pod factory (refugium, rubble, macro) because a "clean" sterile tank starves them; if you can"t keep pods crawling on the glass, you will be fighting a losing battle.
- Tankmates need to be gentle and non-competitive: tiny gobies, small blennies, mandarins in big established systems; avoid wrasses, dottybacks, hawkfish, puffers, and anything that rushes food or nips fins.
- Watch for bloat and snout damage - they can gulp air at the surface and get buoyancy issues, and they can scrape their snout on coarse rock; keep surface agitation modest and use softer, less jagged rockwork.
- They stress out fast in bright, busy setups, so add shaded areas and keep hands out of the tank; once they stop hunting, weight loss happens quick and it can be hard to turn around.
- Breeding is cool if you can get a settled pair: the male carries the eggs, and you will need clouds of tiny live prey for the fry (think copepod nauplii rotifer-sized) from day one or you will lose the batch.
Compatibility
Good Tankmates
- Small, calm gobies like neon gobies (Elacatinus) or clown gobies (Gobiodon) - they tend to mind their own business and do not outcompete Southwell's pipefish at feeding time if you target feed the pipefish
- Tiny captive-bred seahorses (Hippocampus spp.) in a low-flow setup - similar pace and vibe, and you can feed them the same kinds of small frozen foods (think enriched brine, mysis bits, copepods)
- Firefish (Nemateleotris) - peaceful, hover-y fish that are not usually pushy, so the pipefish can cruise and hunt without getting bullied
- Very peaceful, low-competition tankmates only; monitor closely for feeding competition.
- Small non-aggressive cardinals like Banggai cardinals - mellow midwater fish that are not constant grazers on pods, so you are not instantly starving your pipefish
- Gentle cleaner-type shrimp like skunk cleaner shrimp or peppermint shrimp - generally fine, and they do not mess with pipefish (just keep an eye out at feeding time because shrimp can mug the food)
Avoid
- Any nippy fish like most damsels and dottybacks - they will harass pipefish, and even a little chasing can keep pipefish from eating enough
- Fast, food-competitive fish like most wrasses (especially sixline), anthias, and many clownfish - they will hoover up everything before the pipefish gets a shot
- Predators or mouthy fish like hawkfish, larger grammas, and big pseudochromis - they may not outright eat the pipefish, but they will stalk, snap at them, or stress them out constantly
- Fast, food-competitive fish that prevent consistent feeding; avoid pod-dependent competitors in small systems.
Where they come from
Southwell's pipefish (Siokunichthys southwelli) is one of those tiny, easy-to-miss marine pipefish that lives around shallow coastal habitats in the Indo-Pacific. Think protected areas with lots of structure: seagrass, macroalgae, rubble, little branching bits where a thin fish can disappear in plain sight.
That background explains pretty much everything about keeping them: they want calm water, tons of hitching spots, and food drifting by all day.
Setting up their tank
If you have not kept tiny pipefish before, treat this as a species tank project. They can live in a community on paper, but in real life they get outcompeted, stressed, and slowly starve. I have had the best results in a quiet, mature nano or small tank where I control every variable.
- Tank size: 10-20 gallons can work for a small group, but bigger is easier to stabilize. Stability beats volume rules with these.
- Tank age: mature system only. You want pods and microfauna already established, not a brand new sterile setup.
- Flow: gentle, indirect flow. Enough to keep oxygen up and food suspended, but not so much that the fish get pushed around.
- Filtration: oversized biological filtration, very gentle mechanical filtration. Cover intakes with a sponge so nobody gets pinned.
- Aquascape: macroalgae, gorgonians (non-stinging types), branching rock, and lots of fine hitching points at different heights.
- Lighting: whatever keeps your macro or refugium happy. They do not need blast lighting, but they do like a day-night rhythm.
Avoid stinging corals and anemones. Pipefish drift, perch, and make bad decisions. A single bad sting can turn into an infection fast.
A refugium helps a lot. Even a hang-on box stuffed with chaeto or ulva will crank out pods and gives you a backup food trickle. I like a sand-free display for cleanliness, but a small rubble zone or macro clump where pods can hide is gold.
Build a feeding station. A little shell, dish, or low-flow corner where food collects lets the pipefish hunt efficiently without you dumping clouds of food into the whole tank.
What to feed them
This is the make-or-break part. Southwell's pipefish are micro-predators. They are not made to chase big meals, and they are not made to eat once a day. They do best with frequent, small feedings of tiny live foods.
- Best staples: live copepods (mixed sizes), live baby brine shrimp (newly hatched), enriched baby brine for older individuals
- Good additions: live adult brine (only if enriched), small live mysids (often too big for tiny individuals), cultured tigger pods
- Sometimes accepted: frozen cyclops, finely chopped frozen mysis, roe - but do not count on it unless you have proof they are eating it
If you are trying to convert them to frozen, do it like you would with picky mandarins: mix frozen micro foods into live, feed in the same spot, and watch the fish. You are looking for snicking and swallowing, not just interest. A pipefish that looks like it is hunting but never bulks up is slowly losing.
Do not buy this species unless you can source or culture live foods. In my experience, people do not lose them suddenly, they lose them quietly over 2-6 weeks because they never ate enough.
Feeding schedule that has worked for me: 2-4 small feedings a day, with at least one being live pods or freshly hatched baby brine. If you can only feed once daily, this is not a great pipefish to gamble on.
How they behave and who they get along with
They are gentle, shy, and kind of funny once they settle in. You will see them hover and perch, then do quick little strikes at passing prey. They are not bold in the way a clownfish is bold. If the tank feels busy, they stay tucked away.
- Best tankmates: other tiny, peaceful fish that do not rush food (small gobies that are not aggressive at feeding time can work), tiny snails and micro hermits
- Avoid: wrasses (even the 'peaceful' ones), dottybacks, most damsels, fast anthias, hawkfish, big peppermint or cleaner shrimp that steal food
- Also avoid: aggressive copepod hunters like mandarins in small systems (you are competing for the same pantry)
Pipefish can do fine in pairs or small groups if food is abundant. If food is tight, they get thin fast and the weakest one fades first.
They like calm areas where they can hang and watch food drift by. If your flow is all gyre and no shelter, they spend too much energy just staying put.
Breeding tips
Like other syngnathids, the male carries the eggs. With Siokunichthys, the whole courtship is subtle. You will usually notice a pair sticking close, and then you spot a male looking a bit fuller in the belly area as he broods.
Raising the babies is the real hurdle. The fry are tiny and need tiny live foods right away. If you are serious, plan on a separate rearing setup and a rotifer/copepod pipeline before you ever see eggs.
- Give them stability and a calm tank. Spawning tends to happen when they are not being harassed.
- Feed heavy with live foods. Conditioning matters more than any temperature trick.
- Have live foods ready for fry: rotifers plus copepod nauplii. Baby brine is often too big at first for very small pipefish fry.
- Use gentle air-driven filtration in a fry tank. Standard overflows and power filters are a blender for newborns.
If you catch a male brooding, resist the urge to mess with him. Netting and transfers can cause premature release or loss of the brood.
Common problems to watch for
Most issues with Southwell's pipefish come down to food, stress, and secondary infections. They are tough enough if they are eating, but they do not bounce back well if they get run down.
- Slow starvation: pinched belly, sharp ridges along the body, less hunting behavior, hanging in one spot all day
- Outcompeted at feeding time: they show interest but never get bites because faster fish vacuum everything
- Snout damage: bumping glass, rough nets, or getting sucked against an intake - then it stops feeding
- Bacterial infections: red patches, cloudy areas, fin erosion - often after a sting or abrasion
- Internal parasites: still eating but getting thinner, stringy poop, fading over weeks
Quarantine is tricky with pipefish because many meds are harsh and they stress easily. If you do QT, keep it calm, mature (seeded biofilter), and be ready with live foods. Observation plus supportive care beats a medicine cocktail.
My personal checklist if one looks off: confirm it is actually swallowing food, check flow (is it being blasted?), check for intake hazards, and look closely at the snout. If the snout is damaged, the priority is low stress and easy access to dense live food at a feeding station.
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