SKU: 23711065178

Horseshoe Crab Limulus Polyphemus

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Description

Horseshoe Crab Limulus PolyphemusHorseshoe Crab (Limulus polyphemus)(Also known as Atlantic Horseshoe Crab, American Horseshoe Crab, or King Crab) OverviewThe Horseshoe Crab (Limulus polyphemus) is an ancient and fascinating marine arthropod, often referred to as a living fossil having remained virtually unchanged for over 450 million years. Despite its name, it is not a true crab, but more closely related to spiders and scorpions. Recognisable by its hard, domed carapace, spiny tail

Horseshoe Crab (Limulus polyphemus)

(Also known as Atlantic Horseshoe Crab, American Horseshoe Crab, or King Crab)

Overview

The Horseshoe Crab (Limulus polyphemus) is an ancient and fascinating marine arthropod, often referred to as a “living fossil” — having remained virtually unchanged for over 450 million years. Despite its name, it is not a true crab, but more closely related to spiders and scorpions. Recognisable by its hard, domed carapace, spiny tail spine (telson), and multiple pairs of legs, this species plays an important ecological role as both a substrate cleaner and sand sifter. While captivating, Horseshoe Crabs grow very large and require specialised care, making them suitable only for experienced aquarists with very large marine systems.

Origin

Native to the western Atlantic Ocean, including the Gulf of Mexico and eastern coast of North America, from Maine to the Yucat√°n Peninsula. Found primarily in shallow coastal waters, sandy lagoons, and estuaries, where they burrow into soft substrates searching for food.

Feeding

Horseshoe Crabs are omnivorous scavengers, feeding primarily on benthic organisms and detritus. In captivity, they require a diet rich in protein and organic material. Feed several times weekly with:

  • Mysis shrimp, krill, or chopped clams
  • Marine pellets and sinking wafers
  • Detritus, leftover food, and organic debris from the substrate
  • Occasional algae-based supplements

They use their legs and mouth appendages to sift sand and locate buried food. A deep, soft substrate is essential for natural foraging behaviour.

Lighting

Low to moderate lighting. Horseshoe Crabs do not rely on light for feeding or activity. Provide subdued illumination and shaded areas to mimic their natural, shallow coastal environment.

Water Flow

Moderate, gentle flow. Ensure adequate oxygenation and stable circulation without excessive current that could disturb the substrate or flip the crab.

Placement & Habitat Setup
  • Provide deep sandy substrate (7–10 cm / 3–4 inches) for burrowing and foraging.
  • Avoid sharp rocks or coarse gravel, which can damage the carapace or legs.
  • Ensure the tank is large enough for movement and full burrow cycles.
  • Keep the environment well-oxygenated and free of debris buildup.
Tank Mates

Caution required. Compatible with:

  • Peaceful, slow-moving fish (gobies, blennies, jawfish)
  • Non-aggressive invertebrates (snails, cucumbers, brittle stars)

Avoid:

  • Predatory fish (triggers, puffers, large wrasses)
  • Crustaceans that may nip at legs or eyes
  • Sharp rock structures that could trap or injure the crab
Aggression

Peaceful. Horseshoe Crabs do not attack other tank inhabitants but may unintentionally disturb corals or rockwork while burrowing.

Experience Level

Advanced.Limulus polyphemus requires very large aquariums, deep sand, and excellent water quality. Most specimens are better suited to public aquariums or large, open marine systems. Juveniles can adapt to home tanks but often outgrow them quickly.

Water Parameters
  • Temperature: 22–27°C (72–81°F)
  • pH: 8.1–8.4
  • Salinity: 1.024–1.026 SG
  • Hardness (dKH): 8–12
  • Ammonia / Nitrite: 0 ppm
  • Nitrate: <10 ppm
  • Tank Size: Minimum 500 gallons (1,900L) for adult specimens; 200 gallons (750L) for juveniles

Stable salinity and oxygen levels are essential, as Horseshoe Crabs are sensitive to rapid environmental fluctuations.

Lifespan & Size
  • Size: Up to 60 cm (24 inches) across including tail spine
  • Lifespan: Up to 20 years in the wild; typically 5–10 years in captivity with proper care
Reef Compatibility

Not reef safe. While peaceful, Horseshoe Crabs can dislodge rocks, overturn corals, and disturb substrate-dwelling invertebrates during feeding. Best kept in fish-only or specialised species tanks with soft sand and minimal rockwork.




⚠️ Important Note

Due to their large adult size and deep-sand habitat requirements, Horseshoe Crabs are not suitable for most home aquariums. Many individuals are sold as juveniles but quickly outgrow standard tanks. Only advanced aquarists with spacious systems or public aquarium setups should attempt long-term care.

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SKU: 23711065178

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KDK in Texas
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Pretty Colors to Encourage Me to Walk!
Size: X-Large, Color: (601) Bittersweet Pink / Stone / Stone
Hum. Extra large does not seem extra large. I have a slender but size 10-10.5 foot. Will keep but was hoping for a looser fit. Bought to match an Under Armour walking outfit.
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Reviewed in the United States on May 16, 2026
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Patti J Fredley
Natrona Heights, US
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Socks
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So cute
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Eric Brockman
Alexandria, US
★★★★★ 5
Real comfort.
Size: Large, Color: (001) Black / Black / Pitch Gray
Second purchase. Good workout sock.
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Reviewed in the United States on May 13, 2026
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Mother of M.M.
West Palm Beach, US
★★★★★ 5
Very nice
Size: Large, Color: (100) White / White / Pitch Gray
I just received these for my son. They are very nice and look sturdy, but he hasn't worn them yet, so I cannot speak to how well they hold up in the wash or when worn. They appear to be the right size and look stretchy, but not the kind of stretchy that feels super tight on the foot (which I don't like). If they wear unusually well or poorly, I will come back and edit this.
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Reviewed in the United States on December 26, 2025
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Noah
Lexington, US
★★★★★ 5
MY FAVORITE SOCKS
Size: Large, Color: (001) Black / Black / Pitch Gray
I bought these originally at my local UA store and had to buy more. They are my favorite daily wear.
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Reviewed in the United States on February 25, 2026

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