Head to head
Redtail Catfish vs Candiru
The redtail catfish and the candiru are both catfish of the Amazon and Orinoco basins, but they could hardly be more different in scale or lifestyle: one is a large, opportunistic predator that outgrows home aquariums, the other a tiny, nearly transparent fish that feeds on the blood of other fish.
| Redtail Catfish | Candiru | |
|---|---|---|
| Scientific name | Phractocephalus hemioliopterus | Vandellia cirrhosa |
| Size | Often exceeds a metre in length | Usually 2.5-7 cm long |
| Diet | Carnivore, eating fish, crustaceans, and other prey | Carnivore, a blood parasite of larger fish |
| Feeding strategy | Opportunistic predator, overpowering prey directly | Enters a host fish's gill cavity and feeds on blood |
| Defining feature | Bright reddish-orange tail | Near-transparent body and backward-pointing gill spines |
| Human relationship | Popular aquarium fish that outgrows most tanks | Subject of an exaggerated urban legend about entering humans |
| Habitat | Rivers and wetlands of the Amazon and Orinoco basins | Slow, sediment-laden rivers of the Amazon and Orinoco basins |
| Conservation status | Least Concern | Not Evaluated |
Redtail Catfish vs Candiru: common questions
Would a candiru ever attack a redtail catfish?
It is not a typical target; candiru parasitise a wide range of fish by entering the gill cavity, but a redtail catfish's size and opportunistic predatory habits make it a far more active threat to other fish than the other way around.
Which of the two is more dangerous to people?
Neither poses a realistic danger to people. The redtail catfish is simply a large fish that can be awkward to handle, while the candiru's reputation for entering humans is almost entirely folklore, with essentially no credible documented cases.
How different in size are these two catfish?
Dramatically different: the redtail catfish often exceeds a metre in length, while the candiru is typically only a few centimetres long, among the smallest catfish found anywhere in the Amazon basin.