Caridina caerulea

This small, shoaling crustacean originates from the ancient lakes of Sulawesi, Indonesia, and is known for its moderate activity and peaceful nature. As a social species, it thrives in groups and feels most secure when kept with several of its own kind. In an aquarium, these shrimp spend their time exploring the bottom and middle areas, constantly searching for food. Their diet is omnivorous, consisting mainly of algae, detritus, and the microscopic biofilm that grows on tank surfaces. This natural foraging can be supplemented with commercial foods like sinking pellets and wafers to ensure a complete diet.

Caring for this species is considered challenging because it requires very specific water conditions. They need warm, alkaline water that is kept stable at all times. Due to these precise needs, they are best suited for experienced aquarists who can provide a dedicated and mature aquarium environment. They remain quite small as adults and have a lifespan of about two years under optimal conditions. Their contribution to the tank's waste is minimal, making them a low-impact inhabitant in a well-managed setup.

Native to the unique, ancient lake systems of Sulawesi, Indonesia, this crustacean belongs to a group of fauna adapted to a highly specific and stable environment. In its natural habitat, it inhabits warm, alkaline waters with low flow and a particular mineral content. Its designation as a vulnerable species underscores the fragility of its native ecosystem and the importance of responsible husbandry. This species exhibits a shoaling nature and should be kept in groups within the aquarium to promote natural behavior and reduce stress. A small group is considered the minimum, with larger colonies being ideal.

Physiologically, this shrimp is well-adapted to its niche. It has a low metabolic rate and consumes little oxygen, resulting in a very low waste output. This low bioload makes it an excellent candidate for specialized nano aquariums, provided its stringent water parameters can be met. In terms of behavior, it is a moderately active, peaceful grazer. With its fusiform body shape, it navigates the bottom and middle swimming zones, meticulously picking at surfaces. As a biofilm consumer, its primary activity involves feeding on the microbial layers covering rocks, wood, and substrate.

Successfully keeping this species is considered difficult and hinges on recreating its natural conditions with precision. A mature, well-established aquarium is essential, as is maintaining stable high temperatures, alkaline pH, and moderate water hardness. Fluctuations in these parameters can be detrimental. The water's total dissolved solids must also be carefully managed. Low water flow is crucial to mimic the calm lacustrine environment they originate from. For diet, while they are exceptional foragers of algae and detritus, their diet should be regularly supplemented with high-quality sinking pellets and wafers to ensure they receive balanced nutrition. Given their specialized needs, a species-only tank is often the most successful approach to long-term care.

Caridina caerulea is a freshwater decapod crustacean belonging to the Atyidae family, a family known for its diverse and often ecologically specialized shrimp species. Endemic to the Malili lake system in Sulawesi, Indonesia, this species is a product of isolated, long-term evolution in an ancient lacustrine environment characterized by stable, warm, and alkaline water chemistry. Its specific epithet, caerulea, hints at its coloration, though its appearance can be variable.

Morphologically, C. caerulea presents a standard caridean body plan, featuring a fusiform or spindle-shaped body that is hydrodynamically efficient for its benthic and near-benthic lifestyle. As an adult, it reaches a modest size, consistent with many other dwarf shrimp species. Its ecological role is that of a primary consumer and detritivore. As an obligate biofilm grazer, it plays a vital part in its native habitat's nutrient cycling by consuming microbial communities that colonize submerged surfaces. This foraging behavior helps control microbial growth and processes organic matter.

Its physiological requirements reflect a high degree of stenotopy, or adaptation to a narrow range of environmental conditions. The species' survival is dependent on a narrow temperature window at the higher end of the typical freshwater spectrum, a high and stable alkaline pH, and a specific range of both general and carbonate hardness. Its metabolism is noted to be low, with correspondingly low oxygen consumption and exceptionally low nitrogenous waste production. This physiological efficiency is likely an adaptation to the stable, oligotrophic-to-mesotrophic conditions of its home lakes. The species' IUCN Red List status as Vulnerable (VU) highlights an elevated risk of extinction in the wild, primarily due to habitat degradation, pollution, and the introduction of invasive species, making ex-situ conservation and responsible captive propagation increasingly important.

The reproduction of this species in captivity is considered difficult and is a significant undertaking that requires special conditions and a dedicated approach. Spontaneous breeding in a community aquarium is highly unlikely due to its stringent requirements for water chemistry and stability. The primary challenge lies in flawlessly replicating and maintaining the warm, alkaline, and moderately hard water parameters of its native Sulawesi lakes, as any deviation can prevent breeding or prove fatal to the offspring.

A dedicated, species-only breeding tank is paramount for success. This setup should be well-matured, containing ample surfaces like porous rock and wood to cultivate the thick biofilm and algae that are essential for fry survival. To differentiate sexes for establishing a breeding colony, females are generally larger and display a deeper, more curved abdomen, or saddle, used for carrying eggs. Males are typically smaller, more slender, and have a straighter underline. Starting with a sizable group is recommended to ensure a healthy ratio of males to females.

This species is an egg-layer that exhibits direct development. After a successful molt and mating, the female will carry a clutch of eggs under her pleopods (swimmerets). She will constantly fan and clean the eggs for several weeks until they hatch. Unlike some other atyid shrimp, Caridina caerulea does not have a free-swimming larval stage that requires brackish water. The young hatch as miniature, fully-formed versions of the adults. These shrimplets are incredibly delicate and immediately begin to graze on microscopic food sources. Their survival is entirely dependent on the stability of the environment and the availability of biofilm. Strong water currents must be avoided, as the fry are easily swept away. While they will primarily feed on the tank's natural microbiome, their diet can be supplemented with specialized powdered fry foods, but dosing must be done with extreme care to avoid fouling the pristine water conditions.