Little Shop of Coral
Emerald Crab (Mithraculus sculptus)
Emerald Crab (Mithraculus sculptus)
Couldn't load pickup availability
The Emerald Crab is a popular clean-up crew crab best known for helping control nuisance algae, especially bubble algae (valonia). It spends most of its time tucked into rockwork, coming out to graze and scavenge. Emerald crabs are reef safe with caution, since they are opportunistic and may pick at corals or small tankmates if underfed or if they grow large.
Why we love it
-
Great helper for nuisance algae control, especially bubble algae
-
Fun, active scavenger that works the rockwork and crevices
-
Useful clean-up crew addition for established reef tanks
Suggested parameters
-
Temperature: 24–26°C (75–79°F)
-
Salinity: 1.024–1.026 SG
-
pH: 8.1–8.4
-
Alkalinity: 8–10 dKH
-
Ammonia/Nitrite: 0
-
Nitrate: Under 20 ppm (stable is best)
Care and placement
-
Difficulty: Easy
-
Reef safe: With caution
-
Placement: Rockwork and caves (mostly nocturnal)
-
Tank maturity: Best in established tanks with available algae and biofilm
Feeding
Emerald crabs will graze algae, but they are also scavengers. In very clean tanks, supplementing helps prevent trouble.
-
Natural grazing: film algae, bubble algae, leftover foods
-
Supplement as needed with nori, algae wafers, or small meaty bits
-
Feed 1 to 3 times per week if algae is limited
-
Underfed crabs are more likely to pick at corals or snails
Compatibility
-
Generally safe with fish and most corals, but monitor behaviour
-
Can pick at small snails, tiny shrimp, or polyps if hungry
-
Avoid housing with aggressive predators (triggers, puffers, larger wrasses)
-
Provide hiding spots, especially around moulting
Important moulting note
Like all crabs, emerald crabs moult. They may hide for a few days and can look “missing” during this time. Leave the shed shell in the tank, it is often eaten and helps recycle minerals.
What you are buying
-
You will receive: 1 Emerald Crab (Mithraculus sculptus)
-
Size and colour can vary between individuals
As with all inverts, slow acclimation is recommended, especially for salinity and temperature.
Collapsible content
LIGHT
LOW: Place coral at the bottom of the tank. Depending on the type, coral may need to be placed off sand and therefore mounted on a ceramic disc of piece of rock.
MEDIUM: Place coral at mid-range of the tank. Best placed/glued on top of a rock scape at mid-range height.
HIGH: Place coral from mid range to just below water level. SPS coral are shallow growing so they require and are able to tolerate intense light.
FLOW
LOW: Most soft coral do well with a small, gentle pulse. There are certain corals that can even be placed in areas of indirect flow, meaning places aside a rock structure or set into a entrance to a cave style space.
MEDIUM: Many LPS types of coral prefer medium pulse current. Most Euphyllia or corals that have more tissue structure connected to their skeleton, don’t like to be in a high flow area like the direct flow of the wave pump.
HIGH: Similar to high light, SPS enjoy being in some heavy current. Most LPS and SPS that branch encrust or plate prefer high flow that simulates the top water waves.
SKILL
ENTRY: While some may say beginner level, "Entry" is a good term to be used when starting out in the world of corals and marine life. Prior to adding livestock, you want to ensure that your reef has the proper parameters including zero levels of ammonia and nitrite. Seeing traces of nitrate in your waters is a good sign - just keep them at a lower level of 2ppm to 10ppm. Maintaining correct temperature and salinity are a huge factor to stable parameters. Starting to monitor your PH, alkalinity, calcium and magnesium is a great habit to get into to keep a successful reef.
While some soft coral don’t require too much light, having a proper reef light that puts out the proper pars is very important. You'll also want to have a good amount of flow and protected rock areas, as placing corals in their happy spot is ideal for success.
ADVANCED: