FISH OF THE WEEK | Pseudomugil cyanodorsalis

This little fish is native to northern and western Australia and parts of southern New Guinea. It’s a euryhaline species meaning it can tolerate a wide range of salinities and has been recorded in full marine conditions as well as pure freshwater environments, and commonly inhabits coastal mangrove creeks and swamps. Such changes may occur on a daily or seasonal basis depending on locality, with some habitats influenced by daily tides whereas others become hypersaline during the dry season before being filled with fresh water when the rains return, for example. Aquatic plants aren’t usually present in its habitat, with substrates tending to be composed of silt and mud, but cover in the form of marginal vegetation or tangles of submerged mangrove roots is common. They feed on floating or suspended zooplankton, phytoplankton, and invertebrates in the wild.

These fish do not grow larger than 1.5 inches (4cm) and are sexually dimorphic- the males being more colorful with blue backs and longer paired fins which are used for display, and the females being a duller gray with white undersides. In the aquarium they like to be kept in shoals of 8+ and are somewhat timid fish. Great additions to any peaceful community brackish or saltwater aquarium.

Sources and further reading: