Spined loach

Geographic Origin and Biotope: Widespread Eurasian species (from Great Britain and Italy to the Amur basin in Russia). Populates the sandy bottoms of slow-flowing rivers, cold streams and mountain lakes.

Taxonomy and Morphology: Spined Loach (Cobitis taenia). Elongated cobitid (up to 12 cm / 4.7 inches). Possesses six tiny barbels and a very small erectile "spine" under the eye that springs out to defend against predators.

Social Behavior: Gregarious (in nature lives in aggregations) and strictly nocturnal. By day it remains motionless buried in the sand or mud (leaving only its eyes emerging), vigorously sifting the bottom at night.

Coloration and Sexual Dimorphism: Perfectly camouflaged: sand-colored back, covered with regular rows of brown dots and spots ("taenia" = ribbon/band). Males smaller and more tapered than adult (swollen) females.

Aquarium Setup: Temperate (non-tropical) tank of at least 100 cm (40 inches). MANDATORY REQUIREMENT: thick and uninterrupted layer of very fine sand. In case of coarse gravel it will not be able to bury itself nor filter and will suffer serious injuries to the snout.

Diet and Feeding: Macrobenthic carnivore. Filters the sand retaining worms and insect larvae and expelling the grains from the gills. In the aquarium it is mandatory to provide bloodworms, tubifex and sinking granular feed at night.

Water Quality: Strictly cold water. Survives between 10 and 22°C (50-71°F, even under ice in winter). The hot summers of 28°C (82°F) typical of tropical aquariums are intolerable and reduce oxygen, killing it by asphyxiation.

Compatibility and Tankmates: Unbelievably peaceful. Insert it only in "Coldwater" setups with cold water fish such as slow ornamental Goldfish (Orandas, if they don't risk swallowing them), White Cloud Mountain Minnows (Tanichthys albonubes) or Rhodeus.

Aquarium Reproduction: Very difficult at home, requires strict observance of cold winter seasons, followed by a thermal rise to 16-18°C (60-64°F). The sticky eggs are deposited among tangles of algae or roots. Fry predated by parents.

Risks and Diseases: Often imported and wrongly sold as a "scavenger" fish for warm aquariums: in these tropical tanks it collapses due to lack of oxygen. Legally protected and endangered species in many European countries due to the destruction of gravel bottoms.