Common Pleco
Hypostomus plecostomus
Also known as: Common plec, Suckermouth catfish, Janitor fish
Quick Facts
- Adult size: 40-50 cm (16-20 inches)
- Minimum tank size: 400 litres (106 gallons)
- Lifespan: 10–20 years
- Temperament: peaceful
- Swimming level: bottom
- Diet: herbivore
- Minimum group size: 1
- Difficulty: intermediate
Water Parameters
- Temperature: 22–28°C
- pH: 6.5–8
- Hardness (GH): 89–357 ppm (5–20 dGH)
Values above are general hardness (GH). For carbonate hardness (KH), the buffer that keeps pH stable, see the water parameters guide.
Care Summary
The fish sold as simply 'pleco' or 'algae eater' at nearly every shop, and one of the most consistently mis-sold animals in the trade. Bought as a 6 to 8cm juvenile to clean a small tank, the common pleco grows relentlessly to 40 to 50cm and produces an enormous bioload, quickly outgrowing and overwhelming the very tank it was meant to maintain. It is hardy in the narrow sense (it rarely gets sick), which masks the real problem: almost nobody who buys one has, or builds, the very large tank it needs. For algae control in a normal home aquarium the bristlenose pleco is the correct fish; the common pleco belongs only in very large setups, or in ponds in suitable climates. Stated plainly, because the size is the entire story.
Tankmates
Peaceful toward fish it cannot fit in its mouth, but its size makes it incompatible with small, slow, or nano species, and its bioload makes it incompatible with small tanks regardless. Suited only to large communities of robust fish, or as a clean-up companion in big cichlid setups. Do not confuse it with the bristlenose pleco: the common pleco reaches 40 to 50cm where the bristlenose stays around 12cm, and the two are sold side by side as juveniles. Known to occasionally rasp the slime coat of flat-bodied, slow fish such as discus and angelfish at night, which can cause sores; the risk drops in well-fed, spacious tanks. Needs driftwood to rasp and a vegetable-led diet.
Compatible with
- Angelfish
- Pearl Gourami
- Boeseman's Rainbowfish
- Tiger Barb
- Clown Loach
- Electric Yellow Cichlid
- Jack Dempsey
- Green Terror
- Severum
Avoid keeping with
Common Problems
- outgrowing the tank (reaches 40-50cm)
- very heavy bioload overwhelming filtration
- being confused with the much smaller bristlenose pleco at purchase
- rasping the slime coat of slow flat-bodied fish like discus
Sources: seriouslyfish.com, fishbase.org · Last updated: 2026-06-20