Rainbow Shark

One of the smallest fish to adopt a “shark” name, Rainbow shark or sometimes known as the red-finned, or ruby shark, is a native to the Southeast Asian freshwaters.

Rainbow sharks are not real sharks. They’re named as such due to the dorsal fin on top of their body that are similar to sharks. 

According to Aquarium Source, these fishes are believed to have originated from the farms of Thailand.


Rainbow fish with the traditional blue and orange colors
Rainbow fish with the traditional blue and orange colors

Photo credit: Merlin Senger  CC-BY-SA-3.0

Rainbow sharks are small 6-inch fishes with red-colored fins and a dorsal fin. These colorful fins stand out vibrantly from their dark-colored body. Females and males can be told apart by their color variations. Males tend to have brighter fins than females. Males also have thin gray lines on their tail fins while this is absent in females.

Behavior – Wild vs Captivity

Rainbow sharks are very popular as aquarium fishes. Captivity, however, encourages behavioral changes in the fish. In the wild, these fish are passive and do not prey or attack other fish and aquatic animals. 

However, when they’re put in an aquarium they turn semi-aggressive and attack other fish in the aquarium. This could be because Rainbow Sharks are territorial fishes and considers any other fish that enters its territory a threat and therefore would attack it. 


Rainbow-shark surrounded by freshwater plants
Rainbow-shark surrounded by freshwater plants

Rainbow Sharks are freshwater fishes and are usually found in the rivers of Southeast Asia, mainly in Myanmar, Thailand, Laos, and Malaysia.


Rainbow Sharks are omnivorous eaters and although they aren’t picky their diet mainly consists of algae, insect larvae, tubifex worms, periphyton, crustaceans, phytoplankton, zooplankton, and aquatic insects. They are known as bottom-feeders.


Rainbow Sharks reproduce by laying eggs and external fertilization. The females first lay eggs and then the males fertilize them by spraying the eggs with his milt. The eggs will then hatch within a week. Their mating time is usually during the month of October – November.

Conservation Status

A Rainbow Shark with lighter colors than the traditional dark body
A Rainbow Shark with lighter colors than the traditional dark body

This species was abundant in the Southeast Asian rivers but their population has declined in recent years according to various articles. Although they are not on any red list, scientists believe that certain dams in rivers have led to decreasing population of these species.  

River dams may decrease floodplains and may therefore interfere with the ruby shark’s breeding patterns.

Interesting Facts

The appearance of al albino Rainbow shark
The appearance of an albino Rainbow shark
  • Albino rainbow sharks are pretty popular because of their beautiful colors. The body of an albino rainbow shark is known to be pink or yellow. This light-colored body contrasts with their bold-colored fins in a unique appearance. 
  • Despite their tiny appearance, rainbow sharks are omnivorous. Which means they will eat both plants and meat that sits on the bottom of the rivers.
  • Rainbow sharks are very popular as aquarium fishes. 
  • Although rainbow sharks are not bred in captivity (aquariums), they are commonly bred in commercial farms. 
  • Rainbow sharks are not social fishes so keeping more than one in a tank usually leads to aggression between them. Two rainbow sharks are not recommended at all. However, a group of five will be fine since one of them will act as a leader and the others will follow.


How big of a tank (aquarium) do you need for a rainbow shark?

Rainbow sharks are very active swimmers and very territorial so a big tank is required if they are to be kept in captivity and to stop them from harming other fishes. A minimum tank size would be 50 gallons. 

Can two rainbow sharks live together?

Rainbow sharks are not social fishes and do not survive well together if only two are present in an area. However, a group of 5 tends to do well as one will act as the leader for the territory and the rest will follow. 

Are albino rainbow sharks aggressive?

Albino rainbow sharks do not typically exhibit aggression but can be a bit too aggressive for the shyer fish species.

How can you tell a male and a female apart in rainbow sharks?

Males and female albino sharks can’t be told apart until they reach maturity. After they reach maturity, they can be told apart by the colors. Males tend to have brighter fin colors than females. Females also have rounder and fuller bellies compared to males. 

Are rainbow sharks endangered?

Although they are not on any endangered list, their population is decreasing due to damming of rivers. 

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