Few-pored wriggler

Where they come from

Few-pored wrigglers (Xenisthmus oligoporus) are one of those tiny, blink-and-you-miss-it reef fish that live in and around rubble and tight crevices. They show up in the Indo-Pacific trade now and then, usually as a surprise hitchhiker type fish rather than something shops can reliably order.

If you have kept small cryptic reef fish before (think tiny gobies and other rubble-dwellers), you will recognize the vibe: they want to be hidden, they want food to drift by, and they do not forgive sloppy acclimation or rough handling.

Setting up their tank

This is an expert fish mostly because it is small, shy, and easy to lose in a big, busy reef. You can keep it in a larger system, but it does way better if you build a section of the tank around it: rubble piles, tight holes, and low-to-moderate flow zones where food can hang for a second.

• Tank size: I would treat 10-20 gallons as a sweet spot if it is a species-focused nano, or a calm corner of a larger reef if you are careful about tankmates
• Rockwork: lots of small caves and interlocking rubble (fist-size rock is not enough - think thumb-size holes and cracks)
• Substrate: fine sand is nice, but rubble patches matter more than sand depth
• Flow: moderate overall, with at least one sheltered eddy where you can target feed
• Lighting: whatever the reef needs; the fish does not care, it just wants shade and cover

Stability matters more than chasing a specific number. Keep salinity steady (an ATO helps a lot), keep nitrate and phosphate in the sane reef range, and avoid sudden swings from big water changes. These fish act fine right up until they do not.

What to feed them

Plan on feeding like you are keeping a tiny, picky micropredator. Most of the time they ignore big chunks and go for small, moving foods. Once settled, they learn the routine, but the first couple weeks can be stressful.

• Best starters: live baby brine (enriched), live copepods, live small mysids if you can get them
• Frozen that often works: cyclops, calanus, finely chopped mysis, fish eggs/roe, enriched brine (as a helper food, not the only food)
• Prepared: some will take tiny pellets eventually, but I would not buy one assuming it will

Target feeding is your friend. I use a small pipette and gently cloud the food right at the entrance to their favorite hole. Do not blast them with a turkey baster. Think: slow drift, repeat a few times.

How they behave and who they get along with

They are cryptic. You will see a quick wriggle, a head poking out, maybe a short dart to grab food, then gone. If you want a fish that cruises the front glass, this is not that fish.

Tankmates are where most people lose them. They are not built for competition. Even fish that are not aggressive can outcompete them at feeding time or spook them into hiding until they slowly waste away.

• Good neighbors: tiny peaceful gobies, small blennies with mellow attitudes, pipefish (if you can feed them), very calm nano reef communities
• Use caution: clownfish, dottybacks, hawkfish, most wrasses, big damsels, big peppermint or cleaner shrimp that steal food
• Avoid: anything that hunts pods hard, anything predatory, and anything that makes you feed heavier food that the wriggler cannot grab

Breeding tips

Breeding is not common in captivity, mostly because people do not keep groups and you rarely even see pairs. They are in the wriggler family (Xenisthmidae), and like a lot of cryptic reef fish they likely spawn in tight shelter with tiny planktonic larvae.

If you want to take a swing at it, your best bet is a species tank with multiple individuals (if you can get them), lots of separated hideouts, and heavy feeding with small live foods. Keep the tank calm and stable for months, not weeks.

Common problems to watch for

The big three problems are starvation, bullying (including passive food competition), and disappearing acts. Because they hide, you can miss the warning signs until the fish is already in trouble.

• Not eating in the first week: try live foods and feed right at the hideout entrance, lights a bit lower, and reduce competition
• Slow weight loss: you are probably feeding foods that are too large or feeding too infrequently for a micropredator
• Gets spooked and never comes out: tankmates too bold, too much traffic at the rockwork, or flow blasting its shelter
• Jumping or ending up in the overflow: gaps in the lid, uncovered weir teeth, or return chambers without guards
• Parasites after shipping: watch for rapid breathing, flashing, and frayed fins - tiny fish can crash fast if you try harsh treatments

My practical rule: if you cannot confidently answer "Did it eat today?" then the setup is not working yet. Once you have a predictable feeding routine where you actually see it take food, they are much less stressful to keep.