Aquarium Catfish Types: Adult Size, Diet and Practical Choices

Aquarium catfish range from tiny grazers to predators longer than a person’s arm. Choose by adult size, social needs and diet—not by the assumption that every whiskered fish cleans the bottom. This guide compares manageable options and explains which familiar shop fish need much more caution.

Cory catfish: social bottom feeders

Many familiar cories reach about 4–7 cm, but species differ. Keep at least six of the same species, with safe substrate and direct feeding. A 20-gallon long is a useful starting point for many common small species; larger relatives need more room. The cory care guide explains species selection and group care.

Glass catfish: feed in the water column

Kryptopterus vitreolus is a shy transparent species reaching roughly 6.5 cm in standard length. Keep at least six in a mature, shaded aquarium with quiet companions. These fish need small foods where they swim, not leftover pellets beneath a cave. Read the glass catfish guide.

Pictus catfish: active and predatory

Pimelodus pictus reaches about 12 cm and needs long swimming space and an appropriate group. Small tetras, guppies and shrimp may be eaten. A roomy aquarium starting around a 120 × 45 cm base is a reference point, with more room for groups and companions. See pictus care before stocking.

Upside-down catfish: a sheltered group

Synodontis nigriventris reaches roughly 9–10 cm and commonly rests inverted beneath wood or leaves. Keep a group, preferably five or more, and provide shaded retreats and varied food. Other fish sold under similar names can grow larger. The upside-down catfish guide covers identification and feeding.

Otocinclus: small grazers for mature aquariums

Several Otocinclus species enter the trade, generally remaining only a few centimeters long. Keep a group with peaceful companions and established grazing surfaces, then verify that they accept supplemental food. Imported fish can arrive severely depleted; they are a poor purchase for cleaning a new tank.

Seriously Fish discusses starvation and identification in O. macrospilus. Our Otocinclus guide provides further care details.

Bristlenose pleco: a smaller alternative

Common domestic Ancistrus reach roughly 10–15 cm. One fish can suit an appropriately sized community more easily than a large common pleco. Provide shelter, vegetable-rich sinking foods and suitable varied supplements. Males can defend caves. See bristlenose care.

Clown pleco: real wood and varied food

Panaqolus maccus remains around 8–10 cm and rasps submerged wood. A 20–30-gallon aquarium with useful floor space can provide a starting home for one fish. Wood must be available, but it is not a complete diet. Read the clown pleco guide for feeding and territory.

Striped Raphael catfish: larger and secretive

Striped Platydoras catfish can approach 20–25 cm and need a substantially larger adult setup than the small species above. They are often hidden by day and may eat mouth-sized companions. Their armor does not make them safe with every predator.

The Platydoras species account also describes trade-name confusion. Verify the actual fish, provide roomy shelters and handle carefully around the defensive spines.

South American bumblebee catfish: identify first

Small Microglanis are secretive predators, usually around 6–9 cm depending on identity and measurement. Similar common names also cover unrelated fish. Provide appropriate companions, group housing where suitable and direct evening feeding. See bumblebee catfish care.

Chinese algae eater: not a catfish

Gyrinocheilus aymonieri belongs to a different fish group. It can become large and territorial, so it should not be sold as an interchangeable substitute for an oto. Seriously Fish records an adult size up to 28 cm in standard length. Review its specific care needs before considering one.

Common plecos: plan a large permanent enclosure

“Common pleco” can refer to several large species that exceed an ordinary community tank’s capacity. Identify the species, plan adult turning space and account for substantial waste. For most aquarists, a correctly chosen smaller species is more manageable. Read the common pleco guide.

Red tail catfish: unsuitable for most homes

Phractocephalus hemioliopterus can exceed a meter and needs a purpose-built adult system on an entirely different scale. A juvenile’s appearance should not determine the purchase. Public aquariums are not guaranteed rehoming destinations. The red tail catfish guide explains the lifetime commitment.

Whichever species you choose, complete the aquarium cycle, quarantine arrivals and make sure every fish eats. No catfish removes the need for cleaning, testing or water changes.