Etroplus suratensis

The Green Chromide, also known as the Pearlspot Cichlid or Karimeen, is a beautiful and distinctive fish from Asia. It has a disc-shaped body with a greenish-gold sheen and is famous for the iridescent 'pearl spots' that dot its sides. It's a brackish water fish, which means it needs an aquarium with a mix of fresh and saltwater to be healthy. Because of this specific need, its large adult size, and its sometimes feisty personality, it is not recommended for absolute beginners.

These are social fish that should be kept in a group, but they will establish a pecking order and can be territorial, meaning they'll guard their own space. A very large tank is necessary to give them enough room to swim and to reduce squabbles. They are not picky eaters and will accept most aquarium foods, but they have a love for vegetation and will likely dig up and eat most live aquarium plants. Due to their tendency to dig, a sandy bottom is a good choice for their tank. As they get older, a pair may form within the group and become dedicated parents if they decide to breed. In short, the Pearlspot is a stunning fish for an aquarist who is ready to manage a large, brackis-water setup and handle a fish with a bit of a personality.

The Green Chromide, Etroplus suratensis, is a fascinating cichlid notable for being one of the few cichlid species native to Asia. Known locally in Kerala, India as 'Karimeen', it holds significant cultural and culinary value. In the aquarium, it's a true brackish water specialist. While juveniles are often found in nearly fresh water, they require increasing salinity as they mature to truly thrive, prevent health issues, and induce breeding. A stable specific gravity, measured with a hydrometer or refractometer, is crucial for their long-term care.

Setting up a proper environment is key to success. The minimum tank size reflects the need to house a small school of these large-bodied fish. A larger footprint is always better to provide ample swimming space and to help dissipate the territorial aggression that is common in the species. Decor should consist of a fine sand or smooth gravel substrate to accommodate their natural digging behavior without causing injury. Create a network of caves and territories using driftwood and large, smooth rocks. Since they are avid plant-eaters and rooters, delicate plants will be destroyed. Robust options like Anubias or Java Fern attached to hardscape might survive, but high-quality artificial plants are a safer alternative. Filtration should be robust to handle their high waste output, but the water return should be diffused to create the low-flow conditions they prefer, mimicking their native estuaries and lagoons.

Socially, E. suratensis is best kept in a group of five or more. Within this group, a dominance hierarchy will form, and eventually, strong monogamous pair bonds will develop. A bonded pair can become highly aggressive towards other fish, especially when preparing to spawn. Tank mates must be chosen with extreme care; they must be large, robust, and also thrive in brackish conditions. Suitable companions include larger Scats, Monos, or Archerfish.

For a balanced diet, their omnivorous nature with a herbivorous leaning should be catered to. A high-quality spirulina-based pellet or flake can serve as a staple. This should be supplemented with frozen foods like mysis shrimp and krill, as well as blanched vegetables such as spinach, zucchini, and peas. This varied diet ensures proper nutrition and enhances their beautiful coloration. Breeding can be achieved by experienced hobbyists. As substrate spawners, a bonded pair will clean a flat surface and lay their eggs. They exhibit exemplary biparental care, diligently guarding the eggs and shepherding the fry once they hatch.

Etroplus suratensis, the type species of its genus, belongs to the subfamily Etroplinae, a small lineage of cichlids endemic to India and Sri Lanka. This geographic isolation makes them of particular interest in the study of cichlid evolution and biogeography, as they represent a distinct radiation separate from the vast African and Neotropical assemblages. Its body morphology is deeply compressiform, an adaptation for maneuverability in structurally complex, low-flow environments like mangrove estuaries and coastal lagoons.

Ecologically, E. suratensis is a euryhaline species, demonstrating remarkable osmoregulatory capabilities that allow it to inhabit a wide spectrum of salinities from freshwater river mouths to hyper-saline lagoons. In its natural biotope, it plays a vital role as a grazer and detritivore. Its feeding habits, which include consuming algae, periphyton (biofilm), and macrophytes, make it an important moderator of primary production within its habitat. The IUCN status of 'Least Concern' reflects a currently stable global population, though localized populations face anthropogenic pressures from habitat degradation and harvesting for aquaculture and the food industry.

In a captive environment, replicating its natural water chemistry is paramount. The required alkaline and very hard water conditions are characteristic of its native estuarine habitats, which are rich in dissolved minerals from both terrestrial runoff and marine influence. The species' high bioload factor is a direct consequence of its substantial adult size and medium metabolic rate. This necessitates a filtration system with a large biological capacity and a high turnover rate to effectively process nitrogenous waste. However, the output must be managed to maintain low-flow conditions, avoiding the high-velocity currents found in riverine systems. Regular, large-volume water changes are non-negotiable for diluting nitrate accumulation and replenishing essential minerals.

Reproductive biology is characterized by monogamous, biparental substrate spawning. Following complex courtship rituals, a bonded pair will select and meticulously clean a spawning site, typically a flat rock or piece of submerged wood. Parental investment is high; both male and female participate in fanning the eggs to ensure oxygenation and defending the clutch and subsequent free-swimming fry from any perceived threats. This advanced parental care strategy is a defining characteristic of the Cichlidae family and significantly increases offspring survivability.