Crayfish Tank Size: Minimum Gallons by Species (With the Footprint Rule)

Crayfish forums love to fight about tank size. One person says 5 gallons is fine, the next says you’re an idiot for using anything under 30. So which is it?

A single crayfish needs at least a 10-gallon tank (the 10-gallon kit I recommend for dwarf crayfish), and 20-30 gallons is ideal for most species. Dwarf crayfish (Cambarellus) can live in 5-10 gallons. Larger species like the Australian yabby need 30-55+.

But raw gallons don’t tell the whole story. Two 20-gallon tanks can have completely different footprints — and crayfish care about footprint, not depth.

Here’s how to actually pick the right tank.

The “1 Inch Per Gallon” Rule Doesn’t Work For Crayfish

You’ll see this rule everywhere: “1 inch of fish per gallon of water.” For crayfish, throw it out.

Crayfish aren’t fish. They don’t swim around using the whole water column. They walk on the bottom, dig in the substrate, and patrol territory.

What matters is floor space — how much ground they can cover without bumping into another crayfish, a glass wall, or a hideout. A 4-inch crayfish in a tall, narrow 10-gallon tank is unhappy even though the math says it fits.

The Footprint Rule (This Is The One That Matters)

Look at the bottom dimensions of any tank you’re considering. That’s the crayfish’s actual living space.

Two tanks can hold 20 gallons of water:

• 24 × 12 × 16 inches → 288 square inches of floor (2 sq ft)
• 30 × 12 × 12 inches → 360 square inches of floor (2.5 sq ft)

Same gallons, very different homes. The 30-inch tank gives 25% more walking room, and that’s what your crayfish will notice.

Rule of thumb: aim for at least 2 square feet of floor space per adult crayfish. More is better.

When you’re shopping, long-and-low beats tall-and-skinny every time. Standard “breeder” or “long” aquariums are great for crayfish. Cube tanks and column tanks are bad.

Tank Size By Species

Crayfish in the pet trade fall into a few genera, and they don’t all need the same setup. Here’s what each one actually wants.

Genus	Common species	Adult size	Minimum tank	Ideal tank
Cambarellus	Dwarf Mexican (CPO), Cajun dwarf	1-2 inches	5 gal	10 gal
Procambarus	Electric Blue, White Specter, Marbled, Self-cloning	4-5 inches	20 gal	29-30 gal long
Faxonius (formerly Orconectes)	Rusty, Virile, Northern crayfish	3-5 inches	20 gal	30 gal long
Cambarus	Common Eastern, Appalachian Brook	3-5 inches	20 gal	30 gal
Cherax	Yabby, Redclaw, Destructor	6-12 inches	30 gal	55-75 gal

A note on what’s not on this list: Macrobrachium is a freshwater prawn genus, not a crayfish, even though pet stores sometimes lump them together. If you have a “long-arm shrimp,” that’s a prawn, and the sizing rules are different.

You Need A Lid. A Real Lid.

This is the single most-overlooked part of crayfish keeping, and the reason people lose pets in the first week.

Crayfish climb out. They climb the filter intake, the heater cord, the airline tubing, the silicone in the corners. Then they fall on the floor and die under the couch.

You need:

• A glass or mesh lid (the lid that actually keeps crayfish from escaping) that covers the entire top
• Cord cutouts sealed with tape or foam
• No gaps wider than the crayfish’s body (which is smaller than you think — they squish)

A 10-gallon tank with no lid is worse than a 5-gallon tank with one. If you’re picking between two options, pick the sealed one.

Bigger Tank = Easier To Keep Alive

This is the part nobody tells beginners. The biggest reason to size up isn’t crayfish happiness — it’s water chemistry.

Crayfish are messy. They tear up plants, scatter food, and produce a lot of waste during molts. A 10-gallon tank goes from “fine” to “ammonia spike” in two days if you miss a water change.

A 20- or 30-gallon tank gives you:

• More water volume to dilute waste
• Slower swings in pH and temperature
• Room for a proper filter (small tanks limit your options)
• Space to add hides without crowding the floor

If you’ve ever lost a crayfish out of nowhere, water quality in a too-small tank is the most likely culprit.

What About Two Crayfish? Or Three?

Short answer: don’t.

Crayfish are territorial, aggressive, and well-armed. They will fight, and after a molt one of them is going to lose limbs or its life.

The “double the space per extra crayfish” rule you’ll see online is misleading. Adding gallons doesn’t make a crayfish stop being a crayfish. Two adults in a 40-gallon tank still find each other.

The only exceptions:

• Dwarf crayfish (Cambarellus) can be kept in small groups in a 20-gallon with lots of hides. They’re peaceful by crayfish standards.
• Berried females with babies — temporary, the babies need to be separated before they’re big enough to fight.

For every other species, plan on one crayfish per tank. If you want two, that means two tanks. Want more detail? I cover this in keeping 2 crayfish together.

What About Baby Crayfish?

Babies (under 1 inch) can live in much smaller setups — a 5-gallon tank handles a clutch of 20-30 juveniles for a few weeks.

But they grow fast, and the cannibalism starts when they hit half an inch. By 1 inch you need to sort them into individual containers or accept heavy losses.

If you’re breeding crayfish on purpose, plan for the grow-out tanks before the babies hatch, not after.

Common Tank-Size Mistakes

Things I see beginners do over and over:

1. Buying a 5-gallon “starter” tank for a Procambarus — it will outgrow it in months.
2. Picking a tall hex tank because it looks cool — useless floor space.
3. Using a tank with no lid because the crayfish is “small” — they all escape.
4. Trying to keep two in a 10-gallon because the pet store said it was fine — it isn’t.
5. Ignoring filtration in a tank too small to hold a proper filter.

Quick Picks By Species

If you’re shopping right now, here’s what fits each species without overthinking:

• Dwarf crayfish (CPO): standard 10 gallon tank with a lid included
• Electric Blue / Marbled / White Specter: 20 gallon long (the size most adult crayfish actually need) or 29 gallon
• Yabby or Redclaw: 40 gallon breeder minimum, 55+ gallon ideal

Whichever you pick, make sure it ships with a lid — and if it doesn’t, add an aquarium lid to the order. That single cheap part will save your crayfish.

Bottom Line

A single adult crayfish needs at least 10 gallons with 2 sq ft of floor space and a secure lid. Most species do better in 20-30 gallons. Dwarf species can go smaller, Australian species need much bigger.

Skip the gallon math and look at the footprint. Then put a lid on it.

Once you’ve picked the tank, the next step is setting it up properly — substrate, filtration, hides, and the cycling everyone skips.