Caridina mariae

This species of Caridina shrimp is a captivating crustacean highly sought after for its unique aesthetics and beneficial role within an aquarium ecosystem. In their natural habitats in Asia, they inhabit cool, clean, slow-moving streams and pools rich in submerged vegetation and leaf litter. Replicating this environment is key to their long-term health. An aquarium should have gentle water flow to avoid stressing them and be well-established with mature biofilm, which serves as a primary food source. As bottom-dwellers, they spend their days meticulously picking at surfaces, a behavior that defines their role as a 'clean-up crew.'

They are social creatures that exhibit more natural and confident behavior when kept in larger groups. A solitary shrimp will often be reclusive and stressed. In a group, they will be seen foraging together throughout the tank. Their diet is omnivorous and should be varied. While they are exceptional consumers of biofilm, algae, and detritus, their diet should be supplemented with high-quality sinking pellets, blanched vegetables, and specialized shrimp foods to ensure they receive all necessary nutrients. Feeding should be regular but controlled, as their low metabolism and waste production mean they contribute very little to the aquarium's bioload, but overfeeding can still pollute the water. Their moderate difficulty rating stems from their need for stable water parameters. They are particularly sensitive to fluctuations in temperature, pH, and hardness, as well as the presence of ammonia, nitrite, and copper. Regular water changes with properly conditioned water are crucial. Due to their small size and peaceful temperament, they are excellent for species-only tanks or community tanks with other small, peaceful fish and invertebrates that will not view them as a food source.

Caridina mariae is a freshwater decapod crustacean belonging to the Atyidae family, a group characterized by chelae (claws) that feature tufts of setae adapted for scraping and filtering fine particulate matter. Native to Asian freshwater systems, this species fills an important ecological niche as a detritivore and primary consumer. Its diet consists mainly of biofilm, algae, and decaying organic matter, making it a key player in nutrient cycling within its benthic habitat. Its IUCN conservation status is listed as Vulnerable, indicating that wild populations face significant threats, which underscores the importance of captive-bred specimens for the aquarium trade.

Morphologically, C. mariae exhibits a compressiform body shape, meaning it is laterally flattened, which allows for maneuverability through dense vegetation and substrate. Its physiology is adapted for stable, temperate environments. It possesses a low metabolic rate and very low oxygen consumption, allowing it to thrive in conditions that are not necessarily oxygen-saturated, provided they are clean and stable. This low metabolism corresponds with a low bioload factor; the species produces minimal waste, having a negligible impact on the nitrogen cycle of a closed system relative to its size. As an arthropod, it undergoes periodic ecdysis (molting) to grow, a process during which it is particularly vulnerable. Successful husbandry requires maintaining specific water chemistry, as the species is intolerant of significant deviations from its preferred soft and slightly acidic to neutral water conditions. Its environmental interactions are primarily centered on its role as a biofilm consumer, constantly grazing on microbial layers that form on all submerged surfaces.

Breeding this shrimp species is considered moderately challenging and is best achieved in a well-established, species-only aquarium to ensure the highest survival rate for the offspring. Success is highly dependent on providing pristine and stable water conditions that replicate their natural habitat. While a specific male-to-female ratio is not strictly necessary, keeping a larger colony of at least ten to twenty individuals naturally provides a healthy mix of both sexes and encourages breeding activity.

Identifying males and females can be done by observing their size and shape. Females are generally larger and more robust than males. The most telling characteristic of a mature female is her curved underbelly, which forms a protected chamber for carrying eggs. Males, in contrast, are more slender and have a straighter, less developed underside. Before mating, a female will molt and release pheromones into the water, signaling her readiness to the males.

After a successful mating, the female will transfer the fertilized eggs to her swimmerets (pleopods), where she will carry and fan them for several weeks to keep them clean and oxygenated. This species undergoes direct development, meaning the eggs hatch into fully formed, miniature versions of the adults, bypassing a larval stage. This simplifies the rearing process as no specialized larval foods are required. The newly hatched shrimplets are extremely small and vulnerable. The primary key to their survival is an abundance of natural food in the form of mature biofilm and algae covering all tank surfaces. This can be supplemented with fine powdered foods designed for shrimp fry. Maintaining immaculate water quality, free from predators and drastic changes, is paramount during this delicate stage to ensure a high yield.