{"product_id":"emerald-crab-mithraculus-sculptus-saltwater-reef","title":"Emerald Crab (Mithraculus sculptus) | Live Saltwater Reef Cleanup Crew, Bubble Algae Eater","description":"\u003cp\u003eThe \u003cstrong\u003eEmerald Crab\u003c\/strong\u003e (\u003cem\u003eMithraculus sculptus\u003c\/em\u003e) is the saltwater hobby's go-to natural predator of \u003cstrong\u003ebubble algae\u003c\/strong\u003e (\u003cem\u003eValonia\u003c\/em\u003e \/ \u003cem\u003eVentricaria\u003c\/em\u003e) — one of the few invertebrates that will actually eat the bubbles whole rather than popping them and spreading them. Hardy, beginner-friendly, and reef safe with caution, a single Emerald Crab is a worthwhile addition to most 20+ gallon reef tanks. Browse our other \u003ca href=\"https:\/\/squeakysaquatics.com\/collections\/salt-water\"\u003esaltwater livestock\u003c\/a\u003e or stock up on \u003ca href=\"https:\/\/squeakysaquatics.com\/collections\/nutrition\"\u003ereef nutrition\u003c\/a\u003e while you're here.\u003c\/p\u003e\n\n\u003ch3\u003eCare Guide\u003c\/h3\u003e\n\u003cp\u003eEmerald Crabs are nocturnal Caribbean reef crabs that hide in rockwork during the day and forage at night. They acclimate easily and tolerate a normal reef parameter range, but — like all marine inverts — they are \u003cstrong\u003eextremely sensitive to copper-based medications\u003c\/strong\u003e and parameter swings. Drip acclimate over 60–90 minutes when introducing.\u003c\/p\u003e\n\u003cp\u003eThe single most important rule: \u003cstrong\u003ekeep them well-fed.\u003c\/strong\u003e A hungry Emerald is a problem Emerald — large or starved specimens will pick at LPS, zoanthids, sleeping fish, or small shrimp at night. A well-fed crab focused on bubble algae and detritus is the textbook reef-safe-with-caution citizen. If your tank is clean of bubble algae and other nuisance algae, supplement with sinking pellets, dried nori, mysis shrimp, or any leftover meaty food.\u003c\/p\u003e\n\n\u003ch3\u003eSpecifications\u003c\/h3\u003e\n\u003ctable style=\"border-collapse: collapse; width: 100%; max-width: 600px;\"\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px; font-weight: bold; width: 40%;\"\u003eScientific Name\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003e\n\u003cem\u003eMithraculus sculptus\u003c\/em\u003e (formerly \u003cem\u003eMithrax sculptus\u003c\/em\u003e)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px; font-weight: bold;\"\u003eCommon Names\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003eEmerald Crab, Green Mithrax Crab, Green Clinging Crab\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px; font-weight: bold;\"\u003eCare Level\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003eBeginner\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px; font-weight: bold;\"\u003eTemperament\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003ePeaceful (when fed); Semi-aggressive when hungry\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px; font-weight: bold;\"\u003eReef Safe\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003eWith caution — keep well-fed\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px; font-weight: bold;\"\u003eTank Size Minimum\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003e10 gallons (20+ gal preferred for reef setups)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px; font-weight: bold;\"\u003eMax Adult Size\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003e~2–2.5 in carapace width (occasionally larger)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px; font-weight: bold;\"\u003eLifespan\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003e2–4 years in captivity\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px; font-weight: bold;\"\u003eWater Type\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003eSaltwater \/ Reef\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px; font-weight: bold;\"\u003eTemperature\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003e72–78°F\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px; font-weight: bold;\"\u003eSalinity (SG)\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003e1.023–1.025\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px; font-weight: bold;\"\u003epH \/ dKH\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003e8.1–8.4 \/ 8–12\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px; font-weight: bold;\"\u003eDiet\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003eOmnivore — bubble algae, hair algae, detritus, leftover meaty foods\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px; font-weight: bold;\"\u003eOrigin\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003eCaribbean Sea, Gulf of Mexico, tropical western Atlantic\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px; font-weight: bold;\"\u003eStocking Density\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003e~1 per 20–30 gallons of reef\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/table\u003e\n\n\u003ch3\u003eCompatibility\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eGreat with:\u003c\/strong\u003e Most reef-safe fish (clownfish, gobies, blennies, firefish, chromis), other CUC species at reasonable density (snails, cleaner shrimp), and the standard mix of LPS, SPS, and soft corals — provided the crab is well-fed.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eUse caution with:\u003c\/strong\u003e Multiple Emerald Crabs in a small tank (food competition can lead to squabbles — stock 1 per 20–30 gallons), small ornamental shrimp, very small or sleeping fish, and tanks with delicate LPS or zoanthid colonies if the crab is large or under-fed.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvoid with:\u003c\/strong\u003e Hawkfish, puffers, triggers, large wrasses, and groupers — these will all happily eat an Emerald Crab. Other large predatory crabs are also a bad mix.\u003c\/p\u003e\n\n\u003ch3\u003eRecommended Foods \u0026amp; Supplies\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/squeakysaquatics.com\/products\/margarita-snail-margarites-pupillus-saltwater-reef-safe-algae-eating-snail\"\u003eMargarita Snail\u003c\/a\u003e — round out your reef cleanup crew with reef-safe algae-eating snails\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/squeakysaquatics.com\/products\/nassarius-snails-large\"\u003eNassarius Snails (Large)\u003c\/a\u003e — sand bed cleaners that handle leftover food the crab misses\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/squeakysaquatics.com\/products\/tiger-sand-snail\"\u003eTiger Sand Snail\u003c\/a\u003e — sand sifters keep the bottom layer aerated\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/squeakysaquatics.com\/products\/scarlet-skunk-cleaner-shrimp-lysmata-amboinensis-saltwater\"\u003eScarlet Skunk Cleaner Shrimp\u003c\/a\u003e — a peaceful tankmate that eats parasites off your fish\u003c\/li\u003e\n\u003cli\u003eBrowse all \u003ca href=\"https:\/\/squeakysaquatics.com\/collections\/nutrition\"\u003enutrition \u0026amp; foods\u003c\/a\u003e — sinking pellets, dried nori, mysis, and frozen options to keep your crab fed\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eFAQ\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eWill it really eat bubble algae?\u003c\/strong\u003e\u003cbr\u003e\nYes — Emerald Crabs are the hobby's most reliable invertebrate predator of \u003cem\u003eValonia\u003c\/em\u003e bubble algae. They puncture the bubble at the base and consume the contents, which keeps reproductive cells contained instead of spreading them across the tank like manual popping does. One crab won't single-handedly clear a heavy infestation overnight, but it will steadily reduce the population alongside good husbandry.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eIs it reef safe?\u003c\/strong\u003e\u003cbr\u003e\nReef safe with caution. Most stay well-behaved when fed, but large, hungry, or older specimens can opportunistically pick at LPS or zoanthids, or grab a small fish at night. The fix is simple: keep them fed. If your tank runs out of nuisance algae and you're not adding supplemental food, expect them to start exploring.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eHow many can I keep?\u003c\/strong\u003e\u003cbr\u003e\nAbout one per 20–30 gallons of reef. Multiple Emeralds in a small tank get aggressive over food and territory. A single crab handles bubble algae duty for most home reefs.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eHow do I acclimate it?\u003c\/strong\u003e\u003cbr\u003e\nDrip acclimate over 60–90 minutes — marine inverts are sensitive to salinity and pH swings. Float the bag for 15 minutes to match temperature, then drip-acclimate to your tank water. Never expose to copper-based medications.\u003c\/p\u003e","brand":"Squeaky's Aquatics","offers":[{"title":"Default Title","offer_id":48252395356379,"sku":"SW4-SW0110","price":9.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0767\/5209\/3403\/files\/emeraldcrab_77940ae9-037d-44a4-8903-4d22c23545e2.png?v=1777984493","url":"https:\/\/squeakysaquatics.com\/products\/emerald-crab-mithraculus-sculptus-saltwater-reef","provider":"Squeaky's Aquatics","version":"1.0","type":"link"}