The Ruby Emerald Crab, a red color variant of Mithraculus sculptus, is a small reef crab known for its deep ruby to burgundy coloration and rounded, slightly hairy body. Like the more common green emerald crab, it has flat, spoon-shaped claws designed for scraping and picking at algae.
Ruby Emerald Crab
$20.00Price
Out of Stock
Tank Size
- 10 gallons minimum
- Larger tanks provide more stable conditions and food sources
Water Parameters
- Temperature: 76–80°F
- Salinity: 1.024–1.026
- pH: 8.1–8.4
- Stable reef conditions are essential
Habitat & Placement
- Provide plenty of live rock for grazing and hiding
- Likes crevices and shaded areas
Diet
- Algae (including film algae and some nuisance algae)
- Detritus
Supplemental Feeding (important if algae is limited)
- Dried seaweed (nori)
- Algae wafers
- Small meaty foods
While they may help with bubble algae, results can vary—some individuals are more effective than others.
Behavior & Compatibility
- Generally reef-safe with caution
- Peaceful when well-fed
- May become opportunistic if underfed:
- Can pick at corals
- May bother slow or weak tank mates
- Best kept with:
- Other invertebrates with caution
Molting
- Will periodically shed its exoskeleton to grow
- During this time, it may hide for several days
- You may see what looks like a “dead crab”—this is usually just a molt
Growth & Lifespan
- Grows to about 2 inches across
- Lifespan: typically 2–3 years in captivity with proper care
Important Notes
- Do not overcrowd—can become territorial with other crabs
- Keep well-fed to reduce risk of coral picking
- Secure rockwork—they can move small pieces while climbing
- Handle carefully—pinching is possible, though usually mild
