Fiddler crab
Minuca minax
Also known as Red-jointed fiddler
Care at a glance
- Temperature
- 75–82°F (24–28°C)
- pH
- 8.0–8.3
- Adult size
- 1.6 in (4 cm)
- Minimum tank
- 10 gal (38 L)
- Temperament
- Mostly peaceful
- Social behavior
- Social
- Swim level
- Bottom
- Difficulty
- Medium
- Breeding
- Hard
- Rarity
- Common
- Origin
- US Atlantic and Gulf coasts (Massachusetts to Texas)
- Family
- Ocypodidae
Overview
Keep them as a small colony, ideally one male with two or three females, in a paludarium of 38 liters or more, since several males packed into a small footprint will fight over burrows and territory. They are mostly peaceful bottom dwellers that dig, forage along the beach, and haul out onto land, and they get along fine with fish but are not a community aquarium fit because of the land and brackish needs. Hold the water at 24 to 28 C, though their temperate to subtropical range means they tolerate cooler room temps and do not need tropical heat, and keep the pH at 8 to 8.3. Feed them sinking pellets, algae, blanched vegetables, and the odd bit of frozen food, and give plenty of hides since a freshly molted crab is soft and vulnerable. Breeding at home is impractical because the larvae need full marine salinity. These are native US wildlife, so do not release captive crabs and check your local rules before collecting.
In the wild
Fiddler crabs live along the US Atlantic and Gulf coasts, from Massachusetts down to Texas, where they burrow in the muddy banks and salt marshes of estuaries. They are semi-terrestrial, so this is not a fully aquatic pet and a plain fish tank will drown it. Set up a paludarium with roughly half land and half water and a sloped beach so the crab can climb out whenever it wants. Give it a few inches of aragonite or coral sand to dig into, which also buffers the water and supplies calcium for molting. Keep the water brackish at a specific gravity around 1.005 to 1.015 with marine salt, hard and alkaline at a pH of 8 to 8.3, and a temperature of 24 to 28 C. A footprint that suits a small group starts at 38 liters, with more floor space added for each extra crab.
Good to know
This is Minuca minax, in the family Ocypodidae, the most freshwater tolerant of the fiddler crabs and the largest in North America. The carapace reaches about 3.7 cm across, with the full leg and claw span running notably wider, and males carry one oversized claw. Even though it pushes far up estuaries, pure freshwater shortens its life to weeks or months, so still keep it brackish. Females release planktonic larvae that need full marine salinity to develop.
Did you know
The oversized claw belongs only to males, and they wave it to court females and warn off rival males, which is where the fiddler name comes from. If a male loses that big claw, the small feeding claw on the other side enlarges to replace it, and the old side regrows as the smaller one.
Keeping Fiddler crab?
Track water tests, reminders and stocking fit.
