Rainbow Shark: Closer to a Minnow Than a Great White

Rainbow sharks (Epalzeorhynchos frenatum) are native to freshwater rivers and seasonal floodplains across Indochina — notably the Mekong, Chao Phraya and Mae Klong basins — including Thailand, Laos and Cambodia, as well as parts of Myanmar and Malaysia.

In the wild, these active swimmers inhabit areas with ample vegetation and natural barriers. In an aquarium setting, they require similar conditions to ensure their well being.

The rainbow shark has a dark, almost black fish's body with vivid red or orange fins. Its cousin, the albino rainbow shark, sports a white body with the same fiery fins, making them standouts in any tank. Despite their name, they are more closely related to minnows than actual sharks.

Rainbow sharks are very active fish and need plenty of swimming space. They are also territorial and can become aggressive, especially toward their own kind or similar-looking bottom dwellers. Providing hiding places and natural barriers like caves and plants helps minimize confrontations.

For a rainbow shark to thrive, you’ll need a large aquarium — a minimum tank size of 55 gallons (208 liters). These fish tend to claim territory, so ample space and distinct hiding spots are essential. A soft, smooth gravel substrate mimics their natural habitat and prevents injury.

Maintain stable water parameters, including:

Regular tank cleaning is a must to prevent disease, including common issues like white spot disease.

As omnivorous fish, rainbow sharks eat a variety of foods. A balanced diet includes high-quality pellets, frozen foods, brine shrimp, plant matter and even algae.

Feed them sparingly and remove uneaten food to keep the tank clean and reduce stress on other fish.

Choosing the right tank mates is critical. While rainbow sharks are active fish, they don’t always play well with others — especially other bottom dwellers or similarly shaped fish.

Avoid placing them with their own kind unless your tank is massive and filled with hiding spaces. Good companions include fast-swimming fish that occupy different water levels.

Breeding rainbow sharks in captivity is rare and challenging. The egg layers typically require very specific water parameters and environmental cues similar to their natural habitat. While it occasionally happens in large public aquariums, successful breeding is unheard of in home tanks.

We created this article in conjunction with AI technology, then made sure it was fact-checked and edited by a HowStuffWorks editor.