𝐏𝐨𝐫𝐜𝐞𝐥𝐚𝐢𝐧 𝐂𝐫𝐚𝐛𝐬

𝐓𝐡𝐞 𝐂𝐨𝐦𝐩𝐥𝐞𝐭𝐞, 𝐍𝐨-𝐃𝐫𝐚𝐦𝐚 𝐆𝐮𝐢𝐝𝐞

Introduction

Alright! Another amazing invertebrate that doesn't get anough love. They are facinating to watch and perfect for smaller tanks with peaceful tankmates or larger tanks when you are okay playing Where's Waldo!

Porcelain crabs are small, steady filter feeders that teach you more about flow and particle dynamics than most gadgets. If you want motion, personality, and low-risk reef drama, they deliver—provided you set up reliable flow lanes and a steady micro-food routine. This article gives you the whole playbook: species ID, tank design, water chemistry, feeding strategy, compatibility, molting, and overall health. If this feels like a lot, take a breath. You’re learning, and that’s what matters. 

Types

There are two main types of porcelain crabs typically found in the hobby.

The first is the anemone porcelain crab (Neopetrolisthes).

Identification: It has a white shell (carapace) with brown spots (sometimes grey) covering it.

Personality: This one hangs out in anemones. Because of that I tend to see mine everyday. I think it just feels safer since it has the protection of the anemone and doesn't feel the need to hide. I have one in my 500g (1892L) reef and it is rare tat it isn't out front and center.

Photo Credit: The Biota Group, Ishrav.in, Quality Marine

The second is the purple zebra porcelain crab (Petrolisthes bolivarensis).

Identification: This one has beautiful purple stripes on its body with a lighter body color underneath. 

Personality: Although I think this crab is stunning, I just never see mine. Even in smaller tanks they just seem to hide quite a bit. Every once in a while I will see it and it will make my day!

Quick Facts

Size: Adult shell width: roughly 1.0–1.6 in (25–40 mm); leg span up to 2.5–3.0 in (64–76 mm) depending on species.

Diet: suspension feeder specializing in microcrustaceans and fine particulates.

Temperament: peaceful with fish, territorial with same-species rivals in tight quarters.

Reef safe: generally safe; may steal food from corals during broadcast feeding. They are not predators, but they are opportunistic competitors for targeted food.

Sensitivities: copper medications, rough handling, rapid salinity changes. Take you time acclimating these. I like to do 60 mins+ in a drip acclimation (1-2 drops per second). Read more about acclimation here if needed.

Typical captive lifespan: about 2–4 years with stable conditions.

Male or Female? Females have a broader abdominal flap and carry eggs beneath it when gravid. Honestly, they are hard to tell apart for me if I don't have several to compare them to.

Fun Fact: Porcelain crabs are not true crabs, but they are still called "crabs". They have three walking leg pairs, a flattened body for wedging into crevices, and oversized claws used mostly for bluff, grip, and shoving—not predation. SO if they aren't crab, what are they??? They belong to the infraorder Anomura, a group that also includes hermit crabs and squat lobsters. They are an example of carcinization, a process where a non-crab lineage independently evolves a crab-like body shape. You can tell them apart from true crabs by their reduced fifth pair of legs, which are typically tiny and tucked under their bodies, and by their long antennae.

Tamara’s Pro Tips: Healthy porcelain crabs grip rock firmly and start fan-feeding soon after they sense food in flow. Limp, non-gripping individuals are a hard pass. Remember, you can always ask you local fish store to feed an animal before you purchase them. Make sure you have whatever food they feed at home, so you can slowly transition them to what you are normally feeding if needed.

Natural History and Behavior

Location: they choose a perch and defend it, especially against conspecifics.

Daily rhythm: brace, extend fans, sweep particles into the mouth, reset. Activity peaks when suspended particulates are present. It feels like watching our crab slowly do Tai Chi. Or maybe quickly do Tai Chi since that is already slow, haha.

Signature trait: feathery mouthpart fans used to sieve particles from moving water. They are simply fascinating to watch and I never get bored of them!

Defense: dropping limbs when grabbed; limbs typically regenerate over successive molts if nutrition and stability are good.

Tamara’s Pro Tips: If a crab relocates repeatedly, it is telling you the flow lane or shelter isn’t right. Adjust pumps by inches, not feet, and re-check.

Tank Requirements

Tank size: a single crab can work in 10–15 gallons; a pair with a stable host anemone is more realistic at 30–40 gallons. I LOVE having a pair in my tank. Honestly, I like everyone in my tank to have a buddy, but these are too cute together. 

Rockwork and shelters: If you opt of the anemone crab, I like to have at least 2 anemones so they can decide which flow works better for them and if you have fish that host the anemone they can each have one. If you opt for the zebra striped one, provide multiple tight, shaded crevices and at least two flat perches intersected by broad, gentle flow. Think of it like a feeding platform they can stand on and filter feed in the gentle flow. Aim for one hiding spot per crab so they can choose their home and be comfortable.

Flow: build a broad, laminar lane that crosses chosen perches. Avoid needle jets that flip crabs; think “moving sidewalk,” not “leaf blower.”

Lighting: match your corals or anemone. The crabs themselves do not require high PAR.

Filtration and nutrients: protein skimming is useful, but do not strip the water. Maintain a modest nutrient floor to keep microfauna available. These guys require a lot of particle suspension for them to be able to snack all day.

Tamara’s Pro Tips: Map your flow lane with a pinch of fine flake or powdered food and watch where it travels. If there isn't already a "perch/feeding station" see if you can make one for them to have the perfect spot in the tank. It also helps make sure you see them everyday.

Feeding Requirements and Techniques

Natural diet: suspended microcrustaceans, fine detrital particles, and similar planktonic fare.

Captive foods: live phytoplankton, live copepods, rotifers, newly hatched enriched Artemia, and high-quality powdered coral foods rehydrated into a thin slurry.

Particle size: sub-1 mm works best; larger chunks are ignored or dropped.

Frequency: two to four small broadcast feedings per day are more effective than one large one. I will often make a mixture of phytoplanton, coral food, and copepods or rotifers and I slowly drip it into my tank throughout the day, using an airline control value. I feed everything live so I don't have to worry about it spoiling. If you are using bottled products just feed faster or put the solution in a cup and put that cup in a small cup of ice.

Pump protocol: do not shut everything off. Keep at least one broad-flow pump on low so food continues to pass the powerheads.

Observation cues: an actively feeding crab extends fans, sweeps, then combs particles into the mouth every few seconds.

Tamara’s Pro Tips: I will often make a mixture of phytoplanton, coral food, and copepods or rotifers and I slowly drip it into my tank throughout the day, using an airline control value. I feed everything live so I don't have to worry about it spoiling. If you are using bottled products just feed faster or put the solution in a cup and put that cup in a small cup of ice. You can also pre-mix a thin slurry and dose in short pulses with a small dosing pump running low.

If the crab stops fan-feeding and starts picking the substrate, your particles are too large or the "feeding lane" is too weak.

Compatibility and Stocking

Good companions: small gobies, clownfish, chromis, dartfish, cardinalfish, most small reef-safe blennies.

Caution: Other porcelain crabs in a smaller tank, hawkfish, larger wrasses, dottybacks in cramped tanks, hungry peppermint shrimp that may harass during molts. Avoid large, opportunistic feeders like triggers, puffers, groupers, and most larger angelfish, which will see the crab as food.

Anemone Associations (Neopetrolisthes)

Best host option in home systems: the bubble-tip anemone (Entacmaea quadricolor). It’s common, hardy by anemone standards, tolerates a wide range of light and flow.

Benefits: a settled bubble-tip provides exactly what a porcelain crab wants—cover, a stable perch right where food is moving, and a predictable flow lane along the tentacles.

Requirements: add the crab only after the anemone has proven it’s done touring the tank. A healthy bubble-tip should be firmly attached, mouth tight, and stationary for at least a couple of weeks with no late-night wanderings. If it’s still walking, your parameters, lighting, or flow aren’t dialed in yet. Fix those first. A roaming anemone hasn’t signed a lease—don’t give it a roommate.

How to introduce the crab: Dim lights 20–30 percent and reduce main flow (not all flow if possible). Place the crab in a small container against the rock at the anemone’s base and let it step out on its terms; do not “set” it on the oral disc like a figurine. You’re aiming for the rock right next to the foot, where flow hugs the tentacles.

Feeding around a host: keep food particle size small and the "feeding lane" the same each time. If you target-feed chunky foods to the anemone, expect the crab to try petty theft. The easy fix is to give the crab a brief micro-food pulse first, then feed the anemone a larger piece; everybody eats, nobody wrestles.

Tamara’s Pro Tips: Keep a spare acclimation box handy; it’s the simplest way to negotiate a truce between a new crab and very proprietary clownfish.

Molting and Shell Health

Frequency: about every 3–8 weeks depending on age and nutrition.

Iodine: Porcelain crabs do need some iodine to help their shells harden. However, avoid blind dosing. If you don’t run ICP tests: don’t dose iodine “just in case.” Iodine is also naturally introduced through a varied diet and regular water changes with a quality salt mix, which is often sufficient for most tanks. Overdosing is far riskier for crustaceans than running slightly low. If you do run ICP: target about 60 µg/L total iodine. If a report shows you’re low, correct gradually using a known-concentration supplement, then re-test in a few weeks rather than guessing day-to-day.

The Molted Shell: Leave the shed shell for 24 hours; the crab often consumes it to reclaim minerals.

Troubleshooting Guide

1. Not fan-feeding after 48 hours.

Increase micro-food density and realign the flow lane across the perch.

2. Getting flipped by pumps.

Shift to a broader, slower lane or move the perch a few inches downstream.

3. Fighting other crabs

Add an equivalent feeding perch and a visual barrier; reduce rival density in smaller tanks.

4. Repeated failed molts

Verify salinity stability, review alkalinity and magnesium, increase feeding frequency; avoid unsupervised iodine dosing.

Frequently Asked Questions

1. Can porcelain crabs live in a low-light soft-coral nano

Yes. Prioritize flow and micro-food over light, as long as corals remain healthy.

2.Will they eat nuisance algae

No. They are filter feeders. They may pick at film for trapped particles, but they are not grazers.

3.Can I keep them with shrimp

Usually yes, but large or hungry shrimp can harass newly molted crabs; provide plenty of hiding spots

4.Are they safe with clams

Generally yes. Avoid placing their preferred feeding perch directly on a mantle edge.

5.Do they need an anemone

No. Hosting benefits Neopetrolisthes, but it isn’t mandatory in home tanks.

6.How many fit in a 20-gallon

One or a bonded pair.

7.Do they scavenge meaty foods

They may pick at fine fragments, but suspended microfoods should be the staple.

8.How quickly should a new crab start fan-feeding

Often within 24 hours if a viable flow lane is present.

9.Will they harm corals

They sometimes steal food; it’s annoying, not destructive.

10.What is the most common reason they fail in home tanks

Underfeeding fine particles. Frequency and particle size matter most once parameters are stable.

11.Can I spot-feed with a pipette

You can, but allowing a fine slurry to drift through a steady lane is usually more effective.

Conclusion

Porcelain crabs reward precision. Give them a stable flow lane, dependable micro-food, and snug shelters, and they will repay you with steady, methodical fan-feeding that doubles as a health check for your reef. If you are excited to try a pair, start with flow planning, build your micro-food routine, and adjust in inches rather than feet.

If you remember nothing else, remember these two things: consistent flow and powdered food. Master that, and your porcelain crab will thrive.

Happy Reefing!