Introduction

The rainbow shark (Epalzeorhynchos frenatus) is a popular freshwater aquarium fish which belongs to the family Cyprinidae under order Cypriniformes of Class Actinopterygii.  It is also referred to as the ruby shark, red fin shark, red finned shark, rainbow shark minnow, green fringelip labeo, whitefin shark and whitetail shark minnow. It is native to the basins of Mekong, Chao Phraya, Xe Bangfai and Maeklong in Thailand and Indonesia. It is found near any type of solid surface at mid water and bottom depths in streams and rivers. It also moves into seasonally flooded habitats and returns to the rivers during dry season.

Rainbow shark’s Overview

It has an elongated body with pointed snout and forked tail. Body is dark black and greenish in color with red fins.  This species has an albino variety with a white body and bright orange fins.  The abdominal area is flat and the linear area from the gill cover, the eye and the mouth has a characteristic brief stripe. Male rainbow shark has brighter coloration and thinner body with black lines along the tail fin. Dorsal, anal and pelvic fins are red with slightly dusky black color. Dorsal fin contains 10-11 branched rays. The rainbow shark prefers water pH, water temperature and water hardness which range from 6.5 to 7.5, 75°F to 80°F and 2 to 15 dH respectively. It feeds on algae, periphyton, phytoplankton and some zooplankton. It can grow up to 22 cm in length and its life span ranges from 5 to 8 years.

Scientific Name: Epalzeorhynchos frenatus

Common Name: Red Fin Shark, Red Shark, Ruby Shark, Albino Rainbow Shark

Origin: Thailand, Indonesia

Adult Size:  up to 22 cm

Behavior: Semi aggressive

Tank Level: Middle to top levels of the tank

Minimum Tank Size:  55 gallons

Diet: Omnivore

Breeding rate: Egg layers, it is difficult to breed in aquarium

Care level: Easy

Water pH: 6.5 – 7.5

Water Hardness: 2 to 15 dH

Water Temperature: 75°F – 80°F

Water Movement: Moderate

Lighting: Moderate to normal lighting

Lifespan:  5 – 8 years.

Background of Rainbow shark

The rainbow shark is originally described in 1934 by H.W. Fowler and it was placed in the genus Labeo under the species name frenatus. In 1998 the species was moved to the present genus Epalzeorhynchos by Yang & Winterbottom. In fact, it is not really shark and actually belongs to the minnow family, Cyprinidae under order Cypriniformes of Class Actinopterygii. It has upright dorsal fin that gives them a shark like appearance.

Housing Rainbow shark

At least 55 gallons or larger tank is recommended and it is arranged with lots of plants and décor. The tank should have much space with plenty of hiding places such as caves, rocks and plants.  Water pH of the tank should be ranged between 6.5-7.5 while water temperature should be varied between 75°F and 80°F and water hardness should be maintained at 2 to 15 dH. Ideally the rainbow shark should be stocked singly due to their territorial nature to same or similar species. Suitable tank mates include fish like barbs, catfish, large tetras and other fish of similar temperament such as rainbowfish, danios, loaches, plecos, rasboras and gouramis.  This fish can become aggressive with other, smaller fish in your tank that invades its territory. They should be kept with at least 5-6 individuals to reduce any aggression and hyper dominance. They should not be kept with other Rainbow sharks and Red Tail Sharks. A tightly fitting lid is highly recommended because they are terrific jumpers. This shark prefers well aerated clean water with high level of dissolved oxygen and moderate water movement.

Feeding Rainbow shark

The rainbow shark is omnivore and in wild, it mainly feeds on algae, periphyton, phytoplankton and some zooplankton. In captive condition, it primarily consumes algae in the form of tablets, wafers and flacks. It also takes live food such as insect larvae, tubifex worms, periphyton, crustaceans, phytoplankton, zooplankton and aquatic insects. It should also be fed with lettuce, spinach and frozen bloodworms and brine shrimp. Feed should be offered 2-3 times per day.

Rainbow shark Breeding

Breeding occurs occasionally in the aquarium due to their aggression towards their own species.   It reaches sexual maturity during the period from October-November. Both male and female need to be at least 4 inches long to ensure sexual maturity. It is an egg layers and spawning season depends on cooler temperatures and day length.

To breed rainbow shark in captive condition hormone injection is used. During spawning in captive condition, the 75 gallons or larger tank is required. At this time the fish should be fed with protein rich food like brine shrimp or tuna and 25 % water of the tank should be changed using bucket. The female lays eggs on the aquarium gravel and the male fertilize them with a milt spray. The eggs should hatch after several days. After fertilization fry should be transferred to 10 gallons fry tank with dechlorinated water and a mini heater. Fry should be fed with liquid fry food for a week to two weeks and then introduce them to baby brine shrimp. The fingerling should be moved to their own tanks when they reach 1/2 to 1 inch long. Juveniles need a lot of vegetation in their diet to promote proper growth and coloration. Without a proper diet their colors fade and their growth is stunted.

Sexing rainbow shark

It is impossible to sex at juvenile stage accurately. Sexually mature females have noticeably thicker body than males. Males are slimmer than the females and have black lines on the anal fin.

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