Gymnorhamphichthys hypostomus

A strange elongated knifefish found through much of the middle Amazon, the Thermometer Knife is a sand dweller, spending much of its time buried in fine sand with just its head visible above the surface. They use their long, sensitive snouts and sensitivity to electrical impulses to find small prey items like worms, insect larvae, and crustaceans buried in the substrate. In the aquarium, they are hardy fish but can easily be outcompeted for food by faster or more aggressive tankmates so are best kept in a species tank or with other peaceful, slow moving species. Like all knifefish, they are primarily active at night but will occasionally emerge during the day to forage and explore. Although two species in the genus Gymnorhamphichthys are often referred to as “thermometer knife”, G. hypostomus is the more commonly seen species in the trade.