Sand knifefish

Care at a glance

Overview

The sand knifefish is a slender, weakly electric fish that spends the daylight hours buried in fine sand and emerges at night to hunt, so its care is really about the substrate. Give it a deep bed of soft, fine sand it can dive into, in a tank of around 200 liters, with dim lighting and calm surroundings. It is peaceful and can be kept singly or as a pair, but it is shy and slow at feeding, so avoid boisterous tankmates that will strip the food before it surfaces; small, very gentle fish are safest, and anything tiny enough to swallow is at risk. Feed small meaty foods after dark, such as micro worms, frozen bloodworm, and other fine sinking items dropped where it forages.

In the wild

This little knifefish lives along the sandy beaches and bars of the Amazon and Orinoco, in places where the bottom is clean, fine sand it can burrow straight into. By day it lies hidden beneath the surface; by night it comes up to forage. Match that with warm water from about 24 to 28 C and a soft, slightly acidic to neutral pH between roughly 5.5 and 7.2. The single most important thing is a deep layer of soft, fine sand with no sharp grains, kept clean. Add gentle flow, dim light, and some wood or leaf litter for extra cover.

Good to know

Gymnorhamphichthys rondoni is a small sand knifefish in the family Rhamphichthyidae, reaching about 15 centimeters, with a translucent, banded body and a long, slender snout. It is weakly electric, like the rest of its family, and uses that sense along with its snout to find food buried in sand. The banded pattern earns it the nickname thermometer knifefish. Breeding is not recorded in the aquarium, so fish are wild caught.

Did you know

It leads a double life tied to the clock: buried out of sight in the riverbed sand all through the day, then rising up to swim and hunt across that same sand once night falls.

Common questions

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