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Species profile

Scarlet Cactus Plecostomus L025

Pseudacanthicus pirarara

Common names: Scarlet Cactus Plecostomus L025, L025, Cactus Plecostomus

Recognized speciesPlecostomus
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Adult size

Up to 45 cm

Typical adult length 33.8–45 cm.

Up to 45 cm

Countries of origin

  • See all stock from Brazil

Good fit for your tank?

Good fit for

  • An experienced keeper with a large predator-style pleco aquarium
  • A single-specimen display with strong filtration
  • A breeder equipped with oversized caves and dividers

Think carefully if

  • You want a peaceful mixed pleco community
  • The aquarium contains shrimp, fry or delicate bottom fish
  • There is no safe way to separate fighting adults
  • You expect it to control algae

Scarlet Cactus Plecostomus L025 is a South American loricariid currently filed as Pseudacanthicus pirarara. Adults reach approximately 45.0 cm. It requires stable, oxygen-rich water, suitable caves, and deliberate feeding.

Appearance and Identification

A very large scarlet cactus pleco with a dark armoured body and vivid red to orange fins. The powerful head, heavy spines and bright fin colour become more dramatic as it matures.

This profile is identified by L025 and the current assignment Pseudacanthicus pirarara. Do not merge it with a visually similar L-number without matching collection locality and diagnostic features.

Mature males generally develop a broader head and stronger odontodes on the cheeks, pectoral fins and body. Females become fuller through the abdomen, but juveniles are difficult to sex.

Tank Requirements

Suggested filter
About 2,000–2,500 litres an hour
Suggested heater
About 500–750 W for this tank
Minimum tank volume
500 litres
Minimum tank length
180 cm
Minimum group size
1
Recommended group size
1
Activity level
Moderate
Flow preference
High
Planting preference
Lightly planted
Hiding places
Yes
Lid recommended
Yes
Jumping risk
Low

Provide a very spacious aquarium with powerful filtration, high oxygenation, stable rockwork and large secure caves. Heavy protein feeding requires strict waste removal, and a secure lid is sensible for a powerful adult.

Behaviour and Tankmates

Predatory, nocturnal and often highly territorial with other loricariids. Adults can inflict serious injuries during disputes over caves, food or floor space.

Best kept singly unless the aquarium is exceptionally large and provides several widely separated territories.

Strongly territorial toward similarly shaped loricariids, especially mature males and fish competing for caves.

Use robust midwater companions and keep other plecos only in exceptionally spacious, divided layouts. Shrimp, snails, fry and weak bottom fish may be eaten or injured.

Check tankmates for this species

Water Parameters

Temperature
25–30 °C
pH
5.5–7.5
GH
1–15
KH
0–7
TDS
40–260
Stability importance
Critical

Maintain stable, clean, oxygen-rich freshwater. Strong filtration and gas exchange are essential because warm water, protein-rich feeding, and loricariid waste can reduce oxygen and impair water quality.

Parameter caveat
Acclimate slowly to changes in temperature and conductivity. Keep ammonia and nitrite at zero, control nitrate, and never allow caves or rockwork to create stagnant waste pockets.

Feeding

Diet types
Carnivore, Omnivore, Predator
Feeding frequency
Daily
Preferred foods
  • Quality carnivore sinking pelletUse a dense sinking food with aquatic animal protein as the staple.
  • Frozen mussel, prawn, or krillOffer clean pieces sized for the fish and remove uneaten remains.
  • Frozen insect larvae or mysisUseful for variety and conditioning without relying on mammalian meat.
  • Occasional algae or fibre waferProvides dietary variety and fibre, but should not replace the protein-rich staple.

Feed a protein-rich diet based on quality carnivore pellets, crustacean and mollusc foods, with some plant matter for variety. It is not an algae-eating cleanup fish.

Feed after lights dim and place food near every occupied cave. Confirm that subordinate fish eat, and remove rich leftovers before they affect water quality.

Breeding

Breeding type
Cave Spawner, Egg Layer
Breeding difficulty
Specialist
Breeding temperature
28 °C
Breeding pH
6.5
Brood or egg count
Usually several dozen large adhesive eggs; exact fecundity varies by species and female size.
Incubation
7 days
Parental care
Paternal care
Baby foods
  • Mature biofilmContinuous grazing supports fry between targeted feeds.
  • Finely powdered sinking foodFeed tiny portions close to the breeding cave several times daily.
  • Newly hatched brine shrimpUseful supplementary protein once fry leave the cave and can take moving prey.

Captive breeding is possible but advanced. The male guards a clutch inside a large cave, while pair aggression, heavy feeding and strict water quality require careful management.

Habitat and Origin

Geographic origin
Amazon Basin, Brazil, South America
Natural habitat
Fast-Flowing Stream, Freshwater River, Freshwater Stream, Rocky Shoreline
Aquarium contexts
Breeding Tank, Freshwater Aquarium, High-Flow Aquarium, Large Freshwater Aquarium, Species-Only Aquarium
Audience level
Specialist

Classification

Profile type
Recognized species
Genus
Pseudacanthicus
Family
Loricariidae
Species group
Fish, Plecostomus
Previous scientific names
Pseudacanthicus sp. (L025), Historic L-number designation retained as a common identifier.

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Snethlage’s Plecostomus L141

Ancistomus snethlageae

Care level
Intermediate
Adult size
13.5–18 cm
Minimum tank
150 litres
Temperature
24–29 °C

Snowball Plecostomus L102

Hypancistrus inspector

Care level
Advanced
Adult size
11.2–14 cm
Minimum tank
90 litres
Temperature
26–31 °C

Sonia’s Plecostomus L137

Hypostomus soniae

Care level
Intermediate
Adult size
22.5–30 cm
Minimum tank
300 litres
Temperature
22–29 °C

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