Feeding Crabs and Crayfish to Freshwater Pufferfish

Macauley Sykes
2 days ago
9 min read

In the wild, many freshwater pufferfish (species like Pao and Tetraodon) spend much of their time hunting crustaceans. These puffer beaks are made for crushing through their hardened carapaces, giving them access to prey that most other fish can’t touch. Crabs and crayfish aren’t just snacks; they’re full of minerals, protein, and the hard texture that keeps those teeth in check.

When we keep puffers in captivity, the same foods can do wonders if they’re offered properly. This guide looks at why crustaceans are so important, how to prepare them safely, and how to fit them into a healthy, responsible feeding plan.

Nutritional Value of Crayfish and Freshwater Crabs

Crayfish and freshwater crabs form a major part of the natural diet of many large pufferfish species, including Tetraodon mbu and Tetraodon lineatus. Their composition places them amongst the most suitable and beneficial foods that can be offered to pufferfish in captivity. They provide high-quality protein, essential minerals, and the hard-shelled structure needed to maintain dental health and natural feeding behaviour.

Both crayfish and freshwater crabs are lean, high-protein foods, typically containing around 16–19 g of protein and about 1 g of fat per 100 g. This composition supports steady growth and tissue repair without contributing to fatty deposits that can develop in puffers, which are fed excessive amounts of oily seafood. Their flesh contains roughly 25–60 mg of calcium and about 200 mg of phosphorus per 100 g, while the shell is far richer in calcium carbonate. When puffers crush and ingest parts of the shell, they absorb some of this calcium, which helps maintain jaw and skeletal strength.

The shell’s chitin content adds natural roughage to the diet, encouraging healthy digestion and supporting beneficial gut bacteria. Crayfish and freshwater crabs also contain vitamin B12, small amounts of vitamins A and E, and trace minerals such as zinc and selenium, all of which contribute to healthy metabolism and immune function.

The recorded presence of thiaminase in freshwater crustaceans is very low and inconsistent. Some crayfish species show trace enzyme activity, while most freshwater crabs contain little or none. Marine crabs, in contrast, tend to contain much higher levels. Although the risk from freshwater species is likely minimal, it remains wise to focus on variety and balance, incorporating plenty of thiaminase-free foods such as earthworms, snails, and non-thiaminase fish.

When sourced and prepared safely, crayfish and freshwater crabs can form the backbone of a balanced diet for larger puffers, providing the nutrition, mineral content, and dental wear that no other food type fully replicates.

Sourcing and Quality Control

Feeding the right type of crustaceans, in the right form, is essential to keeping pufferfish healthy, but the way these foods are sourced, handled, and prepared matters just as much as their nutritional value.

Whole prey or pieces

Whenever possible, we should feed whole crayfish or freshwater crabs. Pufferfish are designed to crush and consume entire crustaceans; it's what they're made for. They eat everything, including the shell, legs, organs, and also the gut content of those other animals.

The soft, pre-shelled pieces (crab legs or peeled tails) that we can pick up from the supermarket make tasty snacks but are nutritionally incomplete. These pieces lack the same roughage, crunch, and minerals that whole prey items provide and are needed to maintain healthy teeth and balanced nutrition.

Match prey size to the fish:

Large species such as T. mbu and T. lineatus can handle adult crayfish or freshwater crabs.
Mid-sized Pao species and juveniles do better with smaller/younger individuals.

Selecting suitable species

For freshwater puffers, use freshwater or low-salinity crustaceans such as crayfish (Procambarus, Cherax, Pacifastacus) and river crabs (Potamonautes). Saltwater species may look similar and are sometimes easier to source at fish counters, but they contain higher levels of sodium, chloride, and iodine that freshwater fish are just not adapted to handle.

Over time, a diet dominated by marine foods can cause mineral imbalances and reduce long-term vitality. For this reason, Pufferfish Enthusiasts Worldwide does not recommend feeding saltwater crustaceans to freshwater species, except in short-term emergencies where no freshwater alternatives are available.

Raw vs cooked

Always choose raw, frozen-thawed crustaceans, not cooked ones.

Many supermarket products - particularly imported crab claws and crayfish tails - are pre-cooked for human consumption.

Being cooked doesn't make these items dangerous (provided they haven't been mixed with sauces), but it does alter the proteins, removes natural fats, and changes the mineral availability, which reduces overall nutritional value for fish.

Raw, frozen-thawed foods retain the natural textures and compositions that puffers need over the long term to support their nutritional requirements.

Wild-caught and invasive options

In many regions, crayfish are an invasive entity, often outcompeting native species within the same ecological niche. Examples include the signal crayfish (Pacifastacus leniusculus) in the United Kingdom and Europe, the red swamp crayfish (Procambarus clarkii) in parts of Asia and North America, and the marbled crayfish (Procambarus fallax virginalis) in regions of Europe, Madagascar, and Japan.

These crayfish can be highly destructive to the environments where they are not native. Harvesting them to eat for ourselves, or to feed to our fish, can greatly benefit the ecosystem they're being removed from, but only when they are obtained through legal, food-grade channels, and frozen before feeding.

Because wild-caught crustaceans are seasonal, availability typically peaks in warmer months and then drops in the winter. Keepers should plan ahead and bulk buy during the warmer months so they have enough to get you through the colder seasons.

Buying safely

Only purchase from licensed suppliers or food-grade fishmongers.

Avoid:

unregulated or bait-caught sources,
specimens from polluted or unknown waters, and
home-trapped crayfish in areas where collection is illegal.

Farmed stock

Farmed species such as Cherax destructor and Procambarus clarkii are often of excellent quality when raised in clean, well-managed facilities on a balanced diet. However, breeding enough at home to sustain large pufferfish is rarely practical because of the space, time, and maintenance involved. Breeding species that are considered invasive in your country or region is strongly discouraged and may be illegal under local legislation.

For most keepers, food-grade farmed or responsibly trapped frozen stock from licensed suppliers remains the most reliable and ethical choice.

Quality and storage checks

Frozen crustaceans should appear intact and smell clean when thawed.
Discard any with sour or ammonia odour, soft spots, or excessive ice crystals.
Portion crayfish or crabs before freezing so each can be thawed only once.
Label each batch with the freezing date and rotate older stock first.

Handled this way, raw frozen crayfish and freshwater crabs maintain nutritional integrity for months and offer a safe, consistent food supply.

Storage, Freezing, and Thawing

Correct storage is essential to keep crustaceans safe and nutritionally sound. Poor freezing or thawing practices can lead to nutrient loss, bacterial growth, and spoilage.

Storage life and temperature

Domestic freezers at –18 °C or below: store up to six months.
Commercial freezers at –20 °C to –25 °C: up to nine months.
Beyond this, some vitamins (A, E) decline, but proteins and minerals remain stable.

Freezing for parasite control

Holding crustaceans at –20 °C for at least seven days kills most trematodes, nematodes, and protozoans that could infect your fish. Remember that freezing does not always eliminate bacteria, so good hygiene practices remain essential.

Thawing safely

Defrost overnight in the refrigerator, or in a sealed container immersed in cool water for one to two hours.
Never thaw at room temperature or under warm water.
Rinse briefly in dechlorinated water and feed immediately.

Preventing freezer burn

Use airtight or vacuum-sealed bags with minimal air. Ice build-up and dry shell patches indicate dehydration, which reduces palatability.

Handled properly, frozen crayfish and freshwater crabs remain fresh, safe, and nutritionally complete for many months.

Live Feeding vs. Frozen-Thawed

Many aquarists assume that feeding live crayfish or crabs is the most natural way to keep puffers stimulated. While it may appear to mimic wild hunting behaviour, the risks of live feeding far outweigh the limited benefits. Feeding frozen-thawed crustaceans achieves the same nutritional goals and provides safer, more humane enrichment.

Risks of live prey

Injury: Crabs and crayfish defend themselves, and we have seen many instances of them injuring fish with their claws, tearing their lips, puncturing their eyes, and causing other serious wounds in confined tanks.
Parasites: Live crustaceans may carry worms or protozoa. Freezing at –20 °C for seven days inactivates most of them.
Stress and welfare: Despite many myths, decapod crustaceans are capable of pain perception. Feeding them alive for entertainment or convenience is both unnecessary and inhumane.

Benefits of frozen-thawed

Equivalent nutrition to live prey.
No injury from live crabs/crayfish.
Minimal parasite risk.
Easier storage and portion control.

Enrichment alternatives

Pufferfish can still hunt naturally without live prey.

Try:

hiding whole crustaceans in the substrate,
wedging them between rocks or décor,
encouraging chasing with tongs

These safe enrichment methods encourage natural foraging and crushing behaviour without exposing fish or prey to harm.

Conclusion

Feeding crayfish and freshwater crabs to pufferfish is not simply a matter of variety. It is a core part of responsible husbandry if they are part of your fish's natural diet.

Whole, shell-on freshwater species such as crayfish and river crabs replicate what puffers eat in nature. They maintain dental health, strengthen bone and muscle structure, and encourage natural hunting behaviour. When sourced responsibly and frozen for safety, they provide the same benefits as live prey without the risks of injury, parasites, or unnecessary suffering.

Good feeding practice is about balance. Crustaceans should form the foundation of a varied diet that also includes worms, molluscs, and thiaminase-free fish. Each meal should contribute not only to nutrition but also to enrichment, giving the puffer an opportunity to use its instincts safely.

Responsible keepers think beyond what the fish will eat today. They plan for seasonal availability, source foods ethically, and store them correctly. Every aspect of feeding - from the choice of prey to how it is thawed and offered - shapes the long-term health and welfare of these remarkable fish.

When handled with care, crayfish and freshwater crabs are not just food. They are the key to maintaining healthy, confident, and truly thriving pufferfish in captivity.

References

1. Nutritional Composition and Food Science

Arbia, W., Arbia, L., Adour, L. and Amrane, A. (2013) ‘Chitin Extraction from Crustacean Shell Waste: Chemical versus Biological Methods’, Food Hydrocolloids, 31(2), pp. 366–377.

Hossen, M.F., Cummins, S.F. and Elizur, A. (2021) ‘Nutritional composition of commercially important crustaceans and molluscs: a review’, Food Chemistry, 360, 130003.

Sriket, P., Benjakul, S., Visessanguan, W. and Kijroongrojana, K. (2007) ‘Comparative study on composition and thermal properties of black tiger shrimp, white shrimp, and crayfish muscles’, Food Chemistry, 103(4), pp. 1199–1207.

Food and Agriculture Organization of the United Nations (FAO) (2003) Fishery By-products: Quality, Safety and Value-Added Utilization. FAO Fisheries Technical Paper No. 431. Rome: FAO.

2. Freezing, Storage, and Parasite Control

European Food Safety Authority (EFSA) (2010) ‘Scientific Opinion on Risk Assessment of Parasites in Fishery Products’, EFSA Journal, 8(4):1543.

Food Standards Agency (FSA) (2020) Freezing of Fishery Products for Parasite Control: Guidance to Food Business Operators. London: FSA.

World Health Organization (WHO) and FAO (2014) Code of Practice for Fish and Fishery Products (CAC/RCP 52–2003, Rev. 2014). Geneva: WHO/FAO Codex Alimentarius Commission.

Food and Agriculture Organization of the United Nations (FAO) (2016) Handling of Fish and Fishery Products: Freezing and Cold Storage. FAO Fisheries Circular No. 1002. Rome: FAO.

Paragonimus Working Group (2008) ‘Freezing and Cooking Effects on Paragonimus metacercariae in Freshwater Crabs’, Tropical Medicine and Health, 36(1), pp. 23–29.

3. Anatomy, Feeding Ecology, and Behaviour

Liem, K.F. (1970) ‘Adaptive significance of intraoral features in the feeding mechanisms of the Channiform fishes’, Journal of Morphology, 132(1), pp. 69–86.

Clements, K.D., German, D.P., Piché, J., Tribollet, A. and Choat, J.H. (2017) ‘Integrating ecological roles and trophic diversification on coral reefs: multiple lines of evidence identify parrotfishes as microphages’, Marine Biology, 164(4), 98. [Cited for comparative reference to crushing dentition and trophic morphology.]

Clark, F.E., Davies, S.L., Madill, R.E. and Waran, N.K. (2018) ‘Environmental enrichment for teleosts: recommendations based on current scientific evidence’, Applied Animal Behaviour Science, 205, pp. 193–200.

4. Welfare, Ethics, and Sentience

London School of Economics and Political Science (2021) Review of the Evidence of Sentience in Decapod Crustaceans and Cephalopod Molluscs. London: LSE Centre for Philosophy of Natural and Social Science.

5. Environmental and Legal Context

Department for Environment, Food & Rural Affairs (DEFRA) (2021) Wildlife and Countryside Act 1981 (Schedule 9): Invasive Non-native Species List. London: DEFRA.

Environment Agency (UK) (2023) Guidance on the Control of Signal Crayfish (Pacifastacus leniusculus). Bristol: Environment Agency.

Marine Stewardship Council (MSC) (2020) Sustainable Seafood Sourcing and Certification Standards. London: MSC.

Reference Notes

All freezing and parasite control recommendations follow EFSA (2010), FSA (2020), and WHO/FAO Codex (2014) standards.
Decapod welfare considerations are derived from the 2021 LSE report commissioned by DEFRA, now recognised in UK and EU animal welfare frameworks.
Nutritional data ranges for protein, fat, calcium, and phosphorus in crustaceans are taken from FAO (2003) and Hossen et al. (2021).
Environmental and legal guidance regarding invasive crayfish follows DEFRA and Environment Agency publications.

Pufferfish Enthusiasts Worldwide