The Emerald Mithrax Crab is a commonly kept crustacean and is widely known for its ability to help control outbreaks of bubble algae in reef aquariums. These crabs are, however, omnivorous and will not hesitate to help clean up any excess or leftover meaty foods or waste that can settle on or in various surfaces of the tank. Emerald Crabs tend to stay hidden away during the day, emerging from small crevices or ledges to hunt and scavenge for algae and other debris at night. Although generally peaceful, in the absence of sufficient food, Emerald Crabs may demonstrate opportunistic behavior and attempt to predate on smaller invertebrates, fishes, and sometimes corals, so it is imperative to keep them well fed in established systems.
Introduction to Emerald Crab (Efficient Algae Controller & Cleanup Crew)
Emerald crabs (Mithraculus sculptus) are hardy, algae-eating invertebrates that play a crucial role in controlling nuisance algae in reef aquariums. Known for their bright green exoskeleton and powerful claws, these scavengers specialize in consuming bubble algae (Valonia spp.), making them a valuable addition to any cleanup crew. These crabs are low-maintenance and adaptable, often seen climbing rock structures or hiding in crevices during the day before emerging to scavenge at night.
Care Requirements
Care Level: Easy – Adaptable and low-maintenance Minimum Tank Size: 10+ gallons Aquarium Setup: Requires ample rockwork for hiding and foraging Emerald crabs are nocturnal scavengers, spending most of the day hiding in rock crevices before emerging at night to graze on algae and organic debris.
Diet & Nutrition
Emerald crabs are omnivorous and require a varied diet to thrive. Diet: Omnivorous – Prefers algae, detritus, and leftover food Recommended Foods: Bubble algae (primary natural food source) Hair algae, film algae, and uneaten fish food Supplemental seaweed and algae-based pellets if algae is scarce If food becomes limited, emerald crabs may opportunistically scavenge, so regular supplemental feeding ensures they remain reef-safe.
Lifespan & Growth Rate
Lifespan: 2-4 years Growth Rate: Moderate – Typically reaches 2 inches across As they grow, emerald crabs shed their exoskeleton through molting, which is a natural process that may make them appear vulnerable for a short time.
Temperament & Compatibility
Temperament: Peaceful to Semi-Aggressive – Generally peaceful but may show territorial behavior if underfed Reef Safe? With Caution – Completely safe for corals but may prey on small invertebrates if hungry Avoid housing them with aggressive crabs, triggerfish, puffers, or large wrasses, as these species may harass or eat them.
Common Challenges & Considerations
Opportunistic Feeding: If food is scarce, they may target small shrimp or slow-moving invertebrates. Territorial in Small Tanks: Best kept in larger systems with plenty of food and hiding spots. Molting Vulnerability: Newly molted crabs hide until their shell hardens, reducing visibility for a short period. To ensure safe and effective cleanup, provide a well-established tank with algae and detritus.
Water Conditions
Temperature: 74-80°F dKH (Alkalinity): 8-12 pH: 8.1-8.4 Specific Gravity: 1.024-1.026
At Top Shelf Aquatics, we take pride in ensuring your order arrives safely and in perfect condition. Here’s everything you need to know about our shipping process:
Livestock Shipping Details
- Flat Rate Shipping:
- $39.99 Out of State
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- Shipping Days: The calendar during checkout determines when your livestock order will arrive. Normally we ship Monday - Thursday via FedEx Priority Overnight.
Orders placed by 2 PM EST Monday - Thursday ship the same day. Orders placed after 2 PM or on Fridays will ship the next business day. - Delivery Times: Most packages arrive by 10:30 AM EST, though remote areas may experience later deliveries.
We take every measure to protect your livestock, including specialized packaging to maintain temperature and safety during transit.
Dead on Arrival (DOA) Policy
In the rare event of a DOA, you must submit a DOA Request within 2 hours of delivery (FedEx posted time). Once submitted, we will issue a replacement or store credit for the livestock. Please note:
- Shipping costs are not included in the credit.
- Refunds are not offered for livestock or shipping.
While we cannot be held responsible for delays caused by mechanical or weather issues, rest assured we’ll do everything possible to make it right!
Reef Guard Protection Plan
For ultimate peace of mind, upgrade to our Reef Guard Protection Plan. With Reef Guard, you’ll enjoy:
- Extended Livestock Guarantee: Coverage for up to 5 days.
- Priority Resolutions: Hassle-free claims with fast resolutions.
- Weather & Shipping Delay Coverage: Includes FedEx lost packages and damages.
Shipping Restrictions
- We currently ship livestock only within the continental U.S.
- Note: Due to Hawaii state law, we are unable to ship corals to Hawaii.
Now’s the perfect time to prepare your aquarium for its new additions. Consider doing a water change and ensuring space is ready. Check out our YouTube channel for detailed care instructions for your new corals!
For any questions or concerns, feel free to reach out to our support team. We’re here to help make your reefing journey a success!
5 Day Reef Guard
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