🦞 How to Set Up a Pet Crayfish Tank

A crayfish is a bold, curious little crustacean with loads of personality, and the first thing to know is that it is almost always best kept one to a tank. Crayfish are territorial and will often fight or even eat tankmates, including other crayfish, so a single crayfish in its own space is the calm, safe choice. Give one crayfish room to roam, places to hide, and clean water, and it will reward you with hours of busy, entertaining behavior.

Tank size and a secure lid

Crayfish roam the bottom rather than swim, so what they want is floor space, not height. A single crayfish needs at least a 20 gallon tank with a generous footprint — only the little dwarf Mexican crayfish is happy in less. Just as important, they are expert escape artists that climb filter tubes and cords right up and out of an open tank. A secure, gap-free lid is essential. A crayfish on the carpet dries out fast, so do not leave any opening it can squeeze through.

Water: clean and cool

Crayfish are messy eaters, so keeping the water clean takes a solid filter plus regular water changes. Most crayfish also prefer it on the cool side and do best at ordinary room temperature without a heater, since a tank that runs too warm stresses them. Steady, clean, cool water keeps a crayfish active and healthy.

Caves, hides and molting

Give your crayfish several caves and hides to retreat into. This matters most during molting, the vulnerable time when a crayfish sheds its old shell and grows a new, soft one and needs to stay tucked away until it hardens. Do not disturb a molting crayfish, and leave the shed exoskeleton in the tank, because crayfish often eat it back to recover the calcium that helps harden their new shell.

Feeding

Crayfish are omnivores and are not fussy. A good diet is sinking pellets, blanched vegetables, and occasional protein such as a small piece of shrimp or fish. Feed modest amounts and remove leftovers so they do not foul the water you are working to keep clean.

Know your local laws

One important point before you buy: some crayfish are invasive, and several states restrict which ones you may keep. One popular type, the self-cloning marbled crayfish, is banned in a dozen or more US states and right across the EU. Always check your local laws before getting a crayfish, and never release a crayfish into the wild, since even a single released crayfish can damage local waterways. If you can no longer keep yours, rehome it responsibly instead.

Quick setup checklist

• One crayfish per tank, since they are territorial
• At least a 20-gallon tank with a wide footprint (the dwarf Mexican crayfish is the exception)
• Secure, gap-free lid, because they climb out
• Solid filter, regular water changes, cool room-temperature water
• Several caves and hides for retreating and molting
• Omnivore diet; leave the shed shell for calcium
• Check local laws; never release into the wild

Crayfish are not quite as hands-off as some tank pets, so if you would like to compare, our low-maintenance pets guide is a good next read, or take our free pet quiz to find the right fit.

🛒 Recommended supplies

Hand-picked gear for this guide. Affiliate links — we may earn a commission. The $/$$/$$$ badges are a rough budget guide, not live prices.

🧽 Cleaning & maintenance

The main job is regular water changes. Each week, use a gravel vacuum (siphon) to remove about 20–30% of the water along with waste from the bottom, then refill with fresh water treated with a dechlorinator so it is safe. Scrape algae off the glass as needed and rinse the filter media in old tank water — never tap water, which kills the good bacteria. Test the water so you can catch problems early. Never do a full strip-down that wipes out the filter bacteria; steady partial maintenance keeps the water stable and your crayfish healthy.

Cleaning supplies for this habitat. Affiliate links — we may earn a commission. The $/$$/$$$ badges are a rough budget guide, not live prices.

⚠️ Common crayfish setup mistakes

Already have one and something feels off? Start here. These catch almost everybody — none of them mean you have done badly, and every one of them is fixable.

What should I know before getting a crayfish tank?

The mistake: Buying a crayfish nobody in the shop identified.

Tank labels like blue lobster or mystery crayfish cover several different species, and some of them are restricted where you live. The marbled crayfish is the one to watch: it clones itself, so one animal quietly becomes dozens that you cannot legally sell, give away or release.

Try this: Ask for the species name before you pay and check it against your state's restricted list. If your crayfish lays eggs without ever having met another crayfish, it is a marbled crayfish — call your state wildlife agency and ask what to do rather than passing it on.

Can I keep a crayfish I caught in a creek?

The mistake: Bringing a crayfish home from a creek.

Once a wild crayfish has been in a tank it can never go back, because tank animals carry diseases that spread through a whole waterway. Many states also restrict moving live crayfish away from the water they came from, and putting one back is against the law in a lot of places.

Try this: Enjoy creek crayfish where you find them and put them back in the same water the same day. If you want one at home, buy a species you are allowed to keep — and once it is yours, it is yours for life.

Can I use tap water for my crayfish tank?

The mistake: Filling the tank straight from the tap.

The chlorine and chloramine in tap water damage a crayfish's gills. It is a common reason a crayfish goes off its food or dies a day or two after a water change, when the water looked perfectly clean.

Try this: Add dechlorinator to every bucket before it goes in, and let the new water sit until it matches the tank's temperature. A bottle costs a few dollars and lasts months.

Why did my crayfish die after molting?

The mistake: Keeping a crayfish in very soft water.

A crayfish rebuilds its entire shell out of calcium at every molt. In very soft water — including RO or distilled water — the new shell stays rubbery and the crayfish gets stuck partway out, which is one of the most common ways a pet crayfish dies.

Try this: Test GH and aim for roughly 6 to 14, with pH between 7 and 8. If your water is soft, a piece of cuttlebone or a mineral supplement made for shrimp and crayfish raises it cheaply. Leaving the shed shell in helps, but it cannot make up for water with no minerals in it.

Why is my crayfish climbing out of the tank?

The mistake: Running a still tank with no surface movement.

Crayfish pull a lot of oxygen out of the water, and still or warm water holds less of it. A crayfish sitting up at the surface or heading over the rim is usually short of oxygen rather than just being adventurous, and out of water it dries out fast.

Try this: Add an air stone, or angle the filter outflow so the surface ripples. Keep the tank at cool room temperature, and while you are there, run a finger round the lid for gaps where cords and filter pipes go in.

❓ Common questions

📚 Where this comes from

We check our care advice against vets, animal charities, and government health guidance. Here is what this page is built on.

Vets, charities & official guidance

• Marbled crayfish legal case study — National Sea Grant Law Center
• EU Regulation 2016/1141 invasive species list — legislation.gov.uk
• Marbled crayfish risk screening — US Fish and Wildlife Service

Keeper & species-community guides

• Blue crayfish care — Aquariadise
• Crayfish and the molting process — Shrimp and Snail Breeder

Checked August 2026. These are other people’s websites, and none of it replaces your own vet — if a pet seems unwell, call one.