Flounders do not belong to the classic aquarium fish; most species live in the sea and become quite large. In the New World, there is the family Achiridae with 35 species in 9 genera, all of which are either euryhalin, i.e. can change freely between fresh and sea water, or live in pure fresh water. This family includes Hypoclinemus mentalis, a freshwater species distributed practically all over tropical South America, which can reach a length of about 20-25 cm. We occasionally import this species in small quantities from Peru.
The colour and pattern can hardly be used for the determination, because it varies enormously and is similar in numerous freshwater-flunder-species. Typical for Hypoclinemus mentalis are the position of the dorsal and anal fin, the presence of a tiny pectoral fin on the eyed side, the many barbels around the head, the snow-white blind side and the large gill opening on both sides of the head.
Some specimens have black spines on the upper side, which remind something of the odontodes of the loricariid catfish. Is this a sexual characteristic? One does not know it…
These freshwater flounders never enter brackish or sea water as far as known. For their well-being they need sandy soil into which they can dig themselves. Flounders are carnivores that feed on all sorts of worms, crustaceans and even small fish, which they capture mainly at night. Possible companion fishes should therefore not be too small (larger than 5 cm). H. mentalis are peaceful among each other and towards fish which are not suitable as food.
For our customers: the animals have code 262193 on our stocklist. Please note that we only supply the wholesale trade.
Text & photos: Frank Schäfer
