Freshwater blenny

Salaria fluviatilis

FreshwaterFish

Care at a glance

Temperature: 54–68°F (12–20°C)
pH: 7.0–8.0
Adult size: 5.9 in (15 cm)
Minimum tank: 25 gal (95 L)
Temperament: Mostly peaceful
Social behavior: Solitary
Swim level: Bottom
Difficulty: Difficult
Breeding: No record
Rarity: Very rare
Origin: Europe, North Africa
Family: Blenniidae

Overview

The freshwater blenny is a territorial bottom fish that is best kept singly or as a single pair, since males defend a home cavity and will spar with rivals. Away from its own kind it is fairly peaceful and ignores fish that stay up in the water, so pick active, cool-water swimmers as companions rather than other floor dwellers. It hunts small living prey and usually refuses dry flake, so feed frozen and live foods such as bloodworms, small snails, shrimp, and insect larvae. It needs cool, clean, oxygen-rich water and a floor of rock and cobbles with plenty of caves and crevices. A tank of 95 liters or larger with a long footprint gives one fish enough territory.

In the wild

This blenny lives in the rivers, streams, and lakes around the Mediterranean, across southern Europe, the Near East, and North Africa, usually in clear, flowing, rocky water. Unlike most of its tropical relatives it is a cool-water fish, so keep it between about 12 and 20 °C and let it run toward the low end in winter. Its native water is hard and alkaline, around pH 7 to 8, so a rocky, cobble floor with steady, oxygen-rich flow and no heat build-up suits it. A summer chiller or a naturally cool room is often needed to hold the temperature down.

Good to know

The freshwater blenny belongs to Blenniidae, the combtooth blenny family, and males reach about 15 cm, larger than the females. Despite its goby-like shape and habits it is a true blenny rather than a goby, with a single long dorsal fin running the length of the back. Spawning follows the usual blenny pattern: a female lays eggs inside a crevice or under a rock, and the male then cleans, fans, and guards the clutch alone until the fry hatch. Reliable breeding in home aquariums is not established, and the fish is considered threatened across much of its range.

Did you know

Almost every blenny species lives in the sea, so the freshwater blenny is a real oddity, spending its entire life in inland rivers and lakes as one of only a handful of truly freshwater members of a large, mostly marine family.