Fish
Rainbow Shark
Epalzeorhynchos frenatum · also called ruby shark, red-finned shark
Patrolling the bottom of a tank with an upright fin and sleek, shark-shaped outline, a rainbow shark is actually a freshwater minnow, a species now Endangered in its native Thailand rivers even as captive-bred individuals remain common worldwide.
Overview
The rainbow shark, Epalzeorhynchos frenatum, is native to the Chao Phraya river basin of Thailand. Its shark-like silhouette, bright red fins against a dark body, and sharp divide between a declining wild population and an abundant captive one make it one of the more conservation-notable fish commonly kept in home aquariums.
A shark in shape only
Despite its name and unmistakably shark-like fin and body outline, the rainbow shark has no real connection to true sharks, belonging instead to the minnow family, a case of common naming built entirely on visual resemblance.
Status
Endangered, with a declining wild population in Thailand due to habitat loss and pollution, even as captive-bred individuals remain abundant in aquariums worldwide.
Rainbow Shark: common questions
Is the rainbow shark actually a shark?
No, despite the name and its shark-like silhouette, it is a freshwater minnow, placed in an entirely different group from true sharks, and its name comes purely from its fin shape and body outline rather than any real kinship.
Why is the rainbow shark endangered if it is so common in aquariums?
Its wild population in Thailand's Chao Phraya basin has declined sharply due to habitat loss and pollution, even though captive-bred individuals remain abundant and widely available in the aquarium trade, a split between a struggling wild population and a thriving captive one.
Can rainbow sharks be kept with other rainbow sharks?
Generally not well; they tend to be territorial toward their own kind and similarly shaped fish, so most keepers recommend keeping only one rainbow shark per tank to avoid repeated aggression.
What does the rainbow shark eat?
It is an omnivore, grazing algae off surfaces and also eating small invertebrates and plant matter as it forages near the bottom of its habitat.