What are Ancistrus catfish?

Common Ancistrus catfish with impressive tentacles, photo: Ingo Seidel

Ancistrus – a species-rich genus of armored catfish

Ancistrus catfish belong to the family of armored catfish (Loricariidae). Characteristic of this group are the bony armor plates instead of “normal” scales and the inferior sucker mouth, with which the animals scrape growth from roots, stones and other surfaces. The genus Ancistrus is widespread in large parts of South America and inhabits very different habitats – from clear, oxygen-rich streams to calmer river sections with roots, leaves and dead wood, and even in residual waters, ponds and puddles.

Most commercially available Ancistrus catfish remain relatively small at 8-12 cm standard length and are considered robust, peaceful catfish that are well suited for many community tanks. In addition to the “Common Ancistrus catfish” ( Ancistrus sp. “Aquarienstamm” ) there are a variety of other species and forms, some of which are referred to by L-numbers or trade names – such as Ancistrus sp. (L 111) or Ancistrus sp. (L 393) .

A filterable overview of described species, undescribed forms and L-numbers can be found in the species list on Ancistrus.at. For more in-depth practical information on keeping and breeding, this page links to the guide “Ancistrus catfish (Ancistrus) in the aquarium: Keeping, care & breeding”.

Typical characteristics of Ancistrus catfish

Ancistrus catfish cannot be confused with other aquarium fish at first glance. Important features are:

• Stocky, slightly flattened body with bony plates (armor) that protects them from injury.
• Sucker mouth on the belly side, with which they scrape algae, growth and food tablets from surfaces.
• “Antennae” on the head: In adult males, the eponymous fleshy tentacles form on the head; in females, they are usually not or only weakly developed.
• Crepuscular and nocturnal lifestyle: During the day, Ancistrus often sit in caves, under roots or in dense vegetation.

The pronounced tentacles of the males in particular have given the Ancistrus catfish their name and make them real character fish in the aquarium. How to distinguish males and females in detail is explained in more detail in the blog article “How do I recognize the sex of my Ancistrus catfish?”.

Male of Ancistrus sp. “Aquarienstamm” / Common Ancistrus catfish, photo: Ingo Seidel

Habitat and origin

In nature, Ancistrus catfish mainly inhabit waters in South America – such as tributaries of the Amazon, Orinoco or Paraná. Depending on the species, they live in clear, oxygen-rich streams with strong currents or in rather calm, weeded areas with roots and leaf accumulations. Common denominator: There are many hard surfaces with growth and hiding places.

This origin is reflected in the demands in the aquarium. Many Ancistrus species cope well with soft to medium-hard water, as long as the water quality is stable, clean and well filtered. Typical areas in which most species feel comfortable are:

• Temperature around 22-27 °C
• pH usually slightly acidic to neutral
• regular water changes

Details may vary depending on the species – this is exactly where the individual profiles on Ancistrus.at help, in which origin, water values and size are compiled for many Ancistrus forms.

Ancistrus catfish in the aquarium: Keeping & setup

Even if Ancistrus catfish are often placed in the tank as a “cleaning crew”, they should primarily be regarded as fully-fledged aquarium inhabitants with their own requirements. A typical Ancistrus catfish aquarium offers:

• Sufficient floor space: A tank from 80 cm in length is usually useful for a pair or a small group, more space is always welcome.
• Structure and hiding places: branched roots, stone structures, clay tubes and special catfish caves. Ancistrus catfish males form territories and use caves for spawning.
• Shady zones: Floating plants or tall plants in the background provide dimmed light, which crepuscular catfish particularly like.
• Fine substrate: Sand or fine gravel reduce the risk of injury to barbels and abdomen.

For detailed practical tips on tank structure, water care, feeding and socialization, it is worth taking a look at the detailed guide “Ancistrus catfish (Ancistrus) in the aquarium: Keeping, care & breeding”. There, many aspects are deepened that are only touched upon here.

Nutrition: More than just “window cleaners”

In the trade, Ancistrus catfish are often sold as “window cleaners” – and yes, they scrape algae from windows and decorations. Nevertheless, they are not machines that solve all algae problems free of charge and on the side. Anyone who considers Ancistrus only as window cleaners, Scheibenknutscher or Scheibenlutscher and does not feed them specifically risks malnutrition and frustration – for both catfish and owner.

A species-appropriate diet includes:

• herbal food tablets / catfish chips with a high fiber content
• Vegetables such as zucchini, cucumber, peppers, pumpkin, blanched spinach
• Leaves (beech, oak, sea almond tree) as an additional source of fiber and growth surface
• some animal food (e.g. Artemia, mosquito larvae) in moderation, depending on the species and stocking

Wooden roots are a must: Many Ancistrus catfish regularly rasp on real wood and thus absorb components that are important for their digestion. If there is a lack of growth and additional food, even “plant-safe” Ancistrus can start to rasp on delicate plant leaves – a topic that is discussed in detail in the blog article “Ancistrus and plants – why some catfish go to plants”.

Reproduction: productive cave breeders

Ancistrus catfish are typical cave breeders. A male looks for a suitable cave, cleans it thoroughly and lures a female into it to lay eggs. After fertilization, the male takes over the brood care, guards the clutch and fans the eggs with fresh water. The larvae initially remain in the cave and feed on the yolk sac before exploring the aquarium as young fish.

Under good conditions and with several caves, a single pair of Ancistrus can spawn regularly – in community tanks this can quickly lead to “catfish surplus”. If you want to breed specifically, you will find many practical tips in the keeping guide “Keeping, care & breeding” and in the blog articles on the topic of “Breeding”.

Ancistrus sp. “Aquarium strain,” juvenile fish, photo: Ingo Seidel

Frequently asked questions about Ancistrus catfish