Loricariids

Loricariids, commonly known as plecos or suckermouth catfish, are a popular family of bottom-dwelling freshwater fish in the aquarium hobby. Belonging to the Loricariidae family, these distinctive fish are easily recognised by their ventral, sucker-shaped mouths, which allow them to attach themselves to aquarium glass, rocks and driftwood.

Unlike bottom-dwelling fish such as Corydoras, which use their barbels to search through the sand for food, Loricariids are primarily grazers. They feed on biofilm and algae growing on hard surfaces, but they do not clean or sift through the substrate.

Loricariid characteristics and sexual dimorphism

The Loricariidae family includes a large number of species with widely varying sizes and behaviours. Their bodies are covered with protective bony plates, while their characteristic suckermouth allows them to cling to surfaces and graze for food.

Sexual dimorphism can be observed in certain Loricariid species. In Ancistrus, commonly known as Bristlenose Plecos, adult males develop distinctive bristle-like tentacles on the upper part of the head. The barbels around the mouth, on the other hand, are sensory organs.

Popular Loricariid and pleco species

There are many Loricariid and pleco species available for freshwater aquariums, with different sizes, diets and behaviours.

• Ancistrus: Commonly known as the Bristlenose Pleco, this small suckermouth catfish is hardy and easy to observe in a planted aquarium. It feeds on algae and biofilm and requires driftwood or roots in the aquarium to aid digestion.
• Otocinclus: Small, peaceful and discreet, Otocinclus catfish stay close to plants and other surfaces covered with biofilm. They are strictly herbivorous and are well suited to small aquariums.
• Baryancistrus: Larger and often colourful, Baryancistrus plecos need plenty of hiding places and enough space to move around. They explore the bottom of the aquarium and graze on biofilm growing on rocks and driftwood. In an aquarium that is too small, males may become territorial and compete for hiding places.
• Peckoltia: These medium-sized Loricariids are generally peaceful and can feed on biofilm as well as small portions of vegetables such as courgette, cucumber and spinach, alongside their regular diet. They like to hide in sheltered areas and tend to remain discreet.
• Farlowella: Long and slender, Farlowella catfish move slowly and feed mainly on biofilm and microalgae growing on driftwood and other aquarium surfaces.
• Hypancistrus: Some Hypancistrus species have a predominantly carnivorous diet. They like to hide in caves and require a suitable protein-rich diet.
• Pterygoplichthys: These large and robust plecos can reach an impressive adult size. They spend much of their time exploring the bottom of the aquarium and produce a significant amount of waste, so they require a spacious, appropriately sized tank.

Loricariid aquarium setup and minimum tank size

A suitable Loricariid aquarium setup should include a smooth, fine or sandy substrate that will not damage the fish, along with driftwood, roots or branches that provide hiding places and surfaces for grazing.

The aquarium should also include sheltered areas, such as caves and hollow pieces of wood, as well as open spaces where the fish can move freely and access surfaces to graze on.

The minimum tank size for Loricariids and plecos depends on the species. Smaller fish such as Otocinclus can be kept in aquariums from around 50 litres, while large species such as Pterygoplichthys require at least 400 litres.

Loricariid and pleco diet

The Loricariid diet varies depending on the species, with some being herbivorous, omnivorous or carnivorous. Herbivorous and omnivorous Loricariids can be fed specialist pleco or Loricariid pellets, along with algae, biofilm and suitable blanched vegetables.

Carnivorous species, including some Hypancistrus, require suitable sources of animal protein, such as bloodworms, shrimp and protein-rich pellets.

Their characteristic suckermouth allows many Loricariids to graze on hard surfaces, where they feed on biofilm and algae.

Some species, such as Ancistrus and Panaque, require driftwood or roots in the aquarium, as they digest these plant fibres as part of their diet.

Loricariid behaviour and compatibility

Loricariids are generally peaceful and discreet bottom-dwelling fish. They can live alongside other freshwater fish when the aquarium provides sufficient space and suitable hiding places.

Some species, such as Baryancistrus, can become territorial, particularly between males. Providing several separate hiding places can help reduce competition and conflicts.

Loricariids spend much of their time near the bottom of the aquarium, grazing on hard surfaces such as rocks and driftwood.

Although many plecos and suckermouth catfish help limit the growth of biofilm and algae on aquarium surfaces, they never replace regular manual aquarium maintenance.