Steatogenys duidae 10–15 cm | Duida Knifefish

Overview

Steatogenys duidae, often sold as the Duida knifefish, is a fascinating South American electric fish prized by advanced aquarists for its unusual shape, graceful swimming style and nocturnal behaviour. Offered here at approximately 10–15 cm, this species is still juvenile/subadult and will continue to develop into a larger, more substantial fish with age. It is a true conversation piece for a carefully planned aquarium.

This species is best suited to a mature, peaceful community or species setup with soft, clean water, subdued lighting and plenty of cover. Like many knifefish, it is primarily active after dark and spends much of the day resting in shaded areas, emerging at dusk to explore and feed. If you are looking for something genuinely different from the usual tropical fish, Steatogenys duidae offers both rarity and character.

We recommend this fish for aquarists with some experience keeping sensitive species and larger, more specialised setups. As with all live fish from Tropical Fish Co, your order is covered by our live arrival guarantee, and we offer fast UK delivery to help ensure your fish arrives in excellent condition.

Care at a Glance

Origin & Natural Habitat

Steatogenys duidae is native to the Amazon basin region of South America, with records associated with the Río Orinoco and surrounding blackwater and soft-water systems in northern South America. In the wild, knifefish of this type are typically found in slow-moving rivers, flooded forest margins, tributaries and calm backwaters where leaf litter, roots and submerged wood provide shelter.

These habitats are often dimly lit, stained by tannins and low in mineral content. The water is usually warm, soft and slightly acidic to neutral. Understanding this natural environment is the key to successful long-term care: the fish will thrive when given a calm, low-stress aquarium that mirrors these conditions as closely as possible.

As an electric knifefish, Steatogenys duidae uses weak electrical signals to navigate and communicate, especially in low light. This makes it particularly sensitive to abrupt changes in water quality, strong currents and overly bright aquascapes. A stable, mature aquarium is essential.

Tank Setup & Water Parameters

For best results, house Steatogenys duidae in a spacious aquarium of at least 300 litres, with more room strongly recommended if keeping it with compatible tank mates. The tank should be long rather than tall, with open swimming space combined with shaded retreats. Soft sand or smooth fine gravel is ideal, as this species may forage close to the substrate and can be stressed by sharp décor.

Provide plenty of driftwood, dried leaf litter, caves, PVC tubes or other secure hiding places. Dim lighting is preferred, and floating plants can help diffuse brightness while creating a more natural feel. A gentle to moderate flow is best; avoid strong currents that may exhaust the fish or disrupt its nocturnal behaviour.

Water quality must be excellent. Keep ammonia and nitrite at zero, and maintain low nitrate through regular water changes and efficient filtration. Because this species is sensitive to sudden changes, all maintenance should be carried out gradually. A tightly fitting lid is important, as knifefish can be powerful and may jump when startled.

Recommended parameters:

• Temperature: 24–28°C
• pH: 6.0–7.5
• Hardness: Soft to moderately soft water is preferred
• Flow: Gentle

Acclimation should be slow and careful. Newly imported knifefish may be shy initially, so give them time to settle with minimal disturbance and subdued lighting. A mature aquarium with stable biology will greatly improve feeding response and long-term health.

Feeding Guide

Steatogenys duidae is a carnivorous knifefish that naturally feeds on small aquatic invertebrates and other meaty prey. In captivity, it should be offered a varied diet of high-quality frozen and live foods such as bloodworm, blackworm, chopped earthworm, brine shrimp, mysis and other suitable meaty items. Some individuals may also learn to take sinking carnivore pellets or wafers, but live and frozen foods should remain the staple.

Feed in the evening or after lights dim, when the fish is most active. Because this species is nocturnal and may be outcompeted by faster tank mates, target feeding can be useful. Remove uneaten food promptly to protect water quality. A varied diet supports colour, condition and natural behaviour.

Avoid relying on flake food or low-protein general diets. This fish is not an herbivore or omnivore, and poor nutrition can lead to slow growth and reduced vitality. Juveniles may feed more readily than adults, so patience and consistency are important.

Tank Mates / Compatibility

Steatogenys duidae is generally peaceful and best kept with calm, non-aggressive fish that will not nip fins, compete aggressively at feeding time or disturb it during daylight hours. Suitable companions include larger tetras, peaceful dwarf cichlids from soft-water setups, Corydoras, peaceful loricariids, hatchetfish and other gentle South American species of appropriate size.

Because this is a nocturnal, shy fish, avoid boisterous community species, fin-nippers and very active midwater fish that may cause stress. It should not be housed with predatory cichlids, aggressive catfish or species likely to view it as prey. Keep only one unless you have a very large aquarium and a clear understanding of knifefish compatibility and territorial behaviour.

When selecting tank mates, think calm, soft-water and similar water chemistry. The best communities are those that leave the knifefish undisturbed and allow it to feed after dark.

Why Buy from Tropical Fish Co

At Tropical Fish Co, we understand that specialist species need specialist care. Our livestock is selected with health, quality and compatibility in mind, and we pack live fish carefully for the journey. With our live arrival guarantee and fast UK delivery, you can order with confidence knowing your fish will be handled professionally from our facility to your door.

We also aim to provide accurate, practical care information so you can set up the right environment before your fish arrives. For a species as distinctive as Steatogenys duidae, preparation makes all the difference. If you can offer stable, soft water, a peaceful tank and a varied meaty diet, this remarkable knifefish can become a long-lived and rewarding centrepiece in a specialist aquarium.