Raising Emerald Crabs

Also known as Mithrax and green clinging crab, the emerald crab is a saltwater species native to the Caribbean. In comparison to other crab species, the emerald is small, reaching up to 2 inches of body length when adult. Raising and caring for an emerald crab is often considered an easy task, but requires some specific conditions.

  1. Reproduction

    • Like other arthropods, the emerald crab undergoes several development stages during its life cycle. After mating, the female releases the larvae, which undergo three to five molts before becoming adults. Do not put juvenile emerald crabs in a tank with fish, as they can become an easy prey to several fish species. When young, emerald crabs require similar temperature, diet and other environmental conditions as adults.

    Water pH and Temperature

    • Throughout their life cycle, emerald crabs require an environment with slightly alkaline water. Optimum pH values of the water for keeping larvae, juvenile and adult emerald crabs fall between 8.1 and 8.4. As a tropical species, the emerald crab prefers warm water, ideally in the range of 70 degrees to 80 degrees.

    Diet

    • Unlike many other crab species, algae constitute the main part of the emerald crab's diet. In fish tanks, algae can overgrow because of warm temperatures and high levels of nutrients found in the fish food. The emerald crab is popular in fish tanks because it eats bubble algae, such as Valonia and Ventricaria, which can overgrow and become plagues.

    Tank Size

    • An emerald crabs requires a 10-gallon tank as a minimum space to live. This species can become more aggressive toward other invertebrates, such as saltwater snails and even other crabs, when reaching the adult age. Therefore, avoid overstocking your fish tank, and only add more crabs to the tanks if the algae supply increases. Ideally, keep one crab per 20 to 25 gallons of water.