Opae Ula / Hawaiian Red Shrimp

Geographical Origin and Habitat: Endemic to the Hawaiian Islands, inhabiting anchialine pools (brackish water pools with subterranean connections to the sea).

Taxonomy: Member of the family Atyidae, genus Halocaridina. Commonly referred to by its Hawaiian name, Opae Ula.

Social Behavior: Highly active and gregarious. Constantly swims and grazes, forming large groups on porous volcanic rock structures.

Coloration and Sexual Dimorphism: Coloration ranges from bright crimson red to pale pink or orange. The color may fade to white under stress or light.

Tank Setup: Extremely easy to house in tanks as small as 10 liters. Provide volcanic rock (lava rock), aragonite sand, and minimal water current.

Diet and Feeding: Herbivore and detritivore. Feeds on bacterial biofilm and microalgae. Needs very little feeding; occasional micro-particles of spirulina are sufficient.

Water Quality: Brackish water with specific gravity between 1.008 and 1.016. Highly tolerant to temperature fluctuations (20-26 °C) and pH variations.

Compatibility and Tankmates: Best kept in large groups. Avoid any fish tankmates as they will easily prey on these small shrimp.

Aquarium Breeding: Spawning in captivity is slow but achievable. Females carry a small batch of large eggs under their abdomen until hatching.

Risks and Diseases: Main risk is overfeeding, which ruins water quality. Copper treatments are highly lethal. Keep lighting moderate to encourage algae.