Blue-eyed Neon

Adults reach about 3.5 cm in length. Their body is bluish-yellow in tone, while the back is bright blue, creating a striking neon effect under certain lighting. The anal and dorsal fins are noticeably elongated, with the dorsal fin positioned close to the tail. When spread, these fins resemble a skirt. Males are usually larger than females and have longer fins.

Pseudomugil cyanodorsalis naturally inhabits the north-western and northern regions of Australia, with some populations also found in southern New Guinea. These fish live in river deltas, coastal lagoons, mangrove swamps, and even marine waters near the shore—an adaptation that explains their ability to tolerate significant changes in water salinity. Their natural habitats typically lack aquatic vegetation and feature mangrove thickets with silty bottoms.

These fish are calm and peaceful. Given their small size, they are compatible only with species of similar size. If the tank contains brackish water, the choice of tank mates becomes very limited. It is recommended to keep them in a group of at least 8–10 individuals of both sexes for optimal well-being.

A small group of Blue-eyed Neons requires a minimum tank volume of 40 litres. The décor can be arranged to your preference. A sandy substrate is recommended, with a few sticks placed to imitate mangrove thickets. There are different views about water parameters, especially regarding salt addition. Long-term observations show that in brackish conditions, these fish are more active, live longer, and breed more readily. An optimal salt concentration is therefore 1 to 10 g/L. Adequate oxygenation and moderate internal water flow simulating tidal movement are important. A tight-fitting lid is essential to prevent jumping.

Blue-eyed Neons accept all appropriately sized foods—dry, live, and frozen—and prefer to feed near the surface. When possible, offer small bloodworms, brine shrimp, and daphnia to ensure balanced nutrition.

Breeding these fish is straightforward and requires no special preparation. Spawning occurs year-round and is triggered by raising the temperature to the upper limit of 28–30°C. Females lay eggs among plants, attaching them with sticky threads. In freshwater, fine-leaved, low-growing plants such as Java moss work well. In brackish water, artificial spawning substrates, including homemade ones, are more practical. The dominant male fertilizes multiple clutches from different females. These fish lack parental instinct and will eat their own eggs after spawning. To preserve fry, remove fertilized eggs promptly to a separate rearing tank with identical water conditions. Fry remain here until they reach a substantial size, usually about six months. This rearing tank should have the same equipment as the main tank except for the filter system; instead, use a simple sponge-filter air-lift, which provides adequate filtration and prevents fry from being sucked in. Incubation takes about 10 days depending on temperature. In the first days, fry need powdered microfood; after a week, offer brine shrimp nauplii.

Health problems usually arise only as a result of injury or inappropriate conditions that weaken immunity and trigger various diseases. At the first signs of illness, check water parameters for dangerous levels of toxic substances (nitrate, nitrite, ammonia, etc.). Once all values are normal, treatment can begin.

When selecting fish, pay attention to their activity and colour vibrancy. Healthy fish should be mobile, free of visible fin damage, ulcers, or white film on the body. Avoid individuals that appear sluggish, hover at the surface, or have clamped fins, as these may indicate stress or hidden disease. Since this is a schooling species, buy a group of 8–10 individuals at once to reduce stress during adaptation to new conditions.