Rainbow Shark: Diet | Size | Breeding | Cost

If you’re anything like me the first thing you’ll be wondering is how the rather cute looking Rainbow Shark (epalzeorhynchos frenatus) got a name that is shared by a ferocious predator of the deep? The second? How you go about caring for these stunning guys and where you can get one?

First things first, the Rainbow Shark is not a member of the shark (chondrichthyes) family but rather of the cyprinidae family which includes species such as carp and minnow. They have the word shark in their title due to their dorsal fins which stand upright, yes you guessed it, like a shark, and hence the name!

Known for their vibrant fins and dark colored bodies the Rainbow Shark is often confused with its close relative the Redtail shark. The Redtail shark, however, as its name suggests, only has a red tail whilst the Rainbow shark has coloration on all its fins. There are also other subtle differences between the two species meaning they should be treat and cared for, as they are, as separate species.

Rainbow Sharks Characteristics and Care Guide

As we have already discussed the Rainbow shark is best known for its beautiful fin coloration, but it is also so much more. They are full of personality, including some pretty high aggression (at times) and incredibly active swimmers for a bottom-dwelling species.

Care wise they have a few requirements that must be met to keep them in optimum health and happiness which is why their care level is described as moderate. However, as long as these are taken care of the Rainbow shark is a doddle to house. Following are a few of the basic requirements that this species will need. We will go into finer detail through the course of this article.

Scientific NameEpalzeorhynchos bicolor
Common NameRedtail shark
Size 7” Max
Care LevelMedium
Water Conditions72-80° F, KH 10-15, pH 6.4-7.6

Rainbow shark v Red tail shark

Colour and Appearance of Rainbow Sharks

Growing up to around six inches in length the Rainbow shark has a long flat stomach, pointed snout with two pairs of barbels and a down-turning mouth. They are grey to black in coloration with bright red/orange fins and have quite large eyes.

In general, the male of the species tends to be more vibrant in color whilst the female is thicker set. This is not, however, an absolute, rather just a rule of thumb. Coloration can depend on the level of care a Rainbow shark is receiving and its general well being within its aquarium. Unhappy Rainbow sharks tend to get stressed and in the process of doing so lose color.

Please note there is a second variety of the Rainbow shark known as the Albino rainbow shark. This variety still has the red/orange fins which are displayed on the standard but is white, rather than black/grey in body color. It also has the trademark pink eye of other albino species and is a rarer find than the standard colored Rainbow shark.

Rainbow Shark Habitat

Rainbow sharks naturally reside in the warm rivers of South-Eastern Asia. They are prevalent in countries such as Thailand in the Mekong, Chao Phraya, Xe Bangfai, and Maeklong. Here they will be located near the river bottom in amongst the sandy substrate.

Living a solitary lifestyle the Rainbow shark, it is believed, only tolerates the presence of others of their species during breeding. This usually takes place during the months of October and November depending on the climate. Breeding is dictated by the season, length of day, and temperature.

Another aspect of Rainbow shark life that is dictated by the season is migration. During the season of flooding, this species migrates into the wetter areas and then recedes back during the dry period with the river. Populations of Rainbow Shark are being monitored by the IUCN Red List as in recent years they have declined.

Food-wise Rainbow sharks in their natural habitats are omnivores that feed on decaying plants, algae, insect larvae, zooplankton, and small chunks of meat that they find. As bottom dwellers they need their food to sink so they can rummage for it on the sandy bottom of the river.

Rainbow Shark Behavior and Temperament

The Rainbow Shark is a bottom-dwelling species that spends the majority of its time resting on the bottom of the aquarium or sifting its way through the sand looking for tasty morsels of food. They are, however, also known to be very active and will spend a fair amount of time swimming around. When they do swim, they are agile and speedy.

Generally, personality-wise, the Rainbow shark is peaceable and will share its aquarium happily with many other freshwater species. They do not, however, feel the same love for others of their own kind or those who also dwell in the lower half of the water space. Rainbow sharks are incredibly territorial and will react to those invading their space aggressively.

Aggression between Rainbow sharks comes in the form of chasing, biting, head and tail butting, and can result in death. This may take the form of chasing until the fish being chased is so stressed that it dies or physical aggression. Either way, it is not a situation to be desired.

Interestingly the aggression in Rainbow sharks grows as they mature. As juveniles, they will more than likely live amicably together in relative peace and harmony. However, as they reach sexual maturity (around four inches in length) that will change and they will no longer tolerate others. For this very reason, it is suggested that you only keep one Rainbow shark per aquarium which we will go into further detail about in the care section.

Rainbow sharks are also incredibly fun to watch as they feed. They have two pairs of short barbels which they use to probe the substrate and scrape food free. Their mouth is down turned to enable them to eat the food they manage to release easily.

Rainbow Shark Care Guide

Regarding care, it would probably be prudent to address the issue of keeping just one Rainbow shark per aquarium first. This is, as explained previously, due to their aggressive nature with each other. However, there are exceptions to this rule and it is entirely feasible to keep multiple together, five being the magic number.

In order to keep multiple Rainbow sharks together, you would need to provide them with plenty of space where they can build their own territories that would not be disturbed. This would require an aquarium of at least six feet in length with a water capacity of 125 gallon or 463 liters. If you cannot do this, do not even consider keeping more than one.

Now we have covered Rainbow shark numbers to keep we should look at the habitat that they require and how to provide it. As stated previously this species is naturally found in running warm rivers where the substrate is soft and sandy. Copying this in the home is not difficult with many community aquariums already being set up this way.

Aquarium size for one Rainbow shark should be 50 gallons plus long with a medium flowing filtration. Air pumps and air stones are also welcomed by this species who enjoy good water flow around them.

The substrate should be sandy or at the very least fine gravel. This will ensure that the Rainbow sharks two pairs of barbels and mouth will not be damaged as they sift through the sand. For more on how to set up an aquarium successfully check out this great Beginners Guide to Starting a Fish Tank.

Water quality is fairly important to the Rainbow shark just as it is to any species of fish in order to prevent disease and illness. The recommended pH for a Rainbow shark aquarium is 6.5 – 7.5 and the KH should be between 10 and 15. Water temperature should be kept somewhere between 72 – 79℉ or 22 – 26℃ which is a fairly common temperature for community aquariums.

Decor-wise, dense vegetation, plants, driftwood, caves, tunnels, and hiding places are all of importance. This is to allow the Rainbow shark to build a territory that it will feel secure within lowering the chances of aggression. Hiding places are of most importance when the Rainbow shark is young as when juvenile hiding is their activity of choice. It is only as they mature that they will become braver, venture to swim around their environment regularly and develop their aggression.

With regards to lighting and keeping your Rainbow in your aquarium, nothing special is required. This species is happy under most standard lighting systems and is not prone to jumping so a standard lid should also suffice. It may, however, be prudent to keep an eye on your Rainbow shark as a new addition to your aquarium as if they are going to attempt a jump it will be now.

Disease and sickness

Rainbow sharks are fairly hardy but not immune to the general illnesses freshwater fish may suffer from. Possible diseases include ich, swim bladder disorder (SBD), fungus, and skin flukes, and nine times out of ten they will be acquired due to bad water quality. For more information on and how to treat freshwater diseases check out our comprehensive guide on tropical fish diseases.

Avoiding disease and illness in a Rainbow shark due to poor water quality is exceptionally simple. You should simply perform regular maintenance and water changes on your aquarium 20 to 25% of the water should be changed out every week and the substrate vacuumed to remove waste.

Do not be fooled into thinking that as a bottom-feeding species the Rainbow shark lessens the need for regular water changes as this is just not true. They do indeed aid in the cleaning of an aquarium but certainly not enough to negate the need for our regular intervention.

Another way to aid in the prevention of any disease or illness that your Rainbow shark may contract is to feed them high quality and a varied diet similar to that of which they would live on in their natural habitat. We will cover suitable foodstuffs and schedule shortly.

When choosing a Rainbow shark for your aquarium you should look for an active and vibrant specimen. Bear in mind that this species coloration develops as they mature so the ones in your local store will not be as bright as they will become.

Please note rainbow sharks for purchase are usually not mature which is why they can be kept together in the same aquariums in aquatic stores. Rainbow shark aggression levels rise as they grow usually reaching optimal aggression at around four inches in length.

In order to minimize aggression between a Rainbow shark and other tank mates, you can try adding the Rainbow last. This may stop them from developing a territory, or too large a territory, and make them more compatible with their tank mates.

Rainbow sharks will need acclimatizing to their new aquarium but are hardy enough for the floating bag method to be used. Simply turn off the lights in your aquarium and float the bag containing your new addition for around twenty minutes.

Then open the bag and add some of the aquarium water to it and leave to float (securing first) for another ten minutes or so. Repeat the addition of water and leave to float approximately three times before finally adding your Rainbow shark to the main body of water. Leave the lights off for a further few hours to enable your Rainbow shark to settle in.

Rainbow Shark Diet

As an omnivore, the Rainbow shark will eat both meat and vegetation when they are offered. They are not fussy eaters, in fact, they will eat most everything so long as it is available from the bottom of the aquarium. The diet of a Rainbow shark should be varied and similar to what they would eat in their natural habitat. This will help ensure that their immune systems are kept healthy and strong and that their coloration is bright and vibrant.

Foods that should be offered to the Rainbow shark include flaked, frozen, pellets, vegetation, and live. Algae (tablet/wafer), insect larvae, crustaceans (frozen/live), zooplankton, spinach, lettuce, zucchini, and peas are all ideal meals. Bloodworm and brine shrimp can also be offered as a natural color enhancing nutrition.

Feeding should be done two or three times giving enough food for them to consume in five minutes total. Be aware that should you not give a varied diet to the Rainbow shark they may become stunted and display poor coloration.

Breeding and Sexual Differences

It is virtually impossible to sex a Rainbowfish as a juvenile and not that much easier when they reach sexual maturity. A general rule of thumb, however, would be that males have a thinner set body, small black lines on their tail fins, and are brighter colored.

Rather than reaching sexual maturity at a particular age, the Rainbow shark reaches it a certain length. This length is believed to be four inches and at this length, they become aggressive and able to breed.

Little is known of the Rainbow Sharks’ breeding habits as they have not been successfully bred in the home environment. The majority of Rainbow shark that we obtain for the aquarium hobby are either wild-caught or exported from Thailand’s large breeding facilities.

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What is known of breeding is that Rainbow Sharks tend to favor October and November and wait for specific temperatures and day lengths. They are an oviparous species with the female laying the eggs and the male fertilizing them by spraying his milt. Eggs hatch within approximately a week and the resulting fry are free swimming.

Despite the non-existent rate of success with home breeding of the Rainbow shark, it doesn’t mean that you can’t try. It is probably not to be recommended though as Rainbow shark need a separate breeding aquarium of around 75 gallons capacity and also a fry tank to raise the resulting offspring in.

You will also need to be sure that you have a male and female Rainbow shark which can only usually be certified by a sexing specialist.

Should you have a definite pair and the aquariums you need the Rainbow sharks should be placed together in the breeding aquarium for around a week to see if they will tolerate each other and if you’re lucky display breeding behavior.

This will show as the pair rubbing together and the female depositing eggs into the substrate. Once they have been fertilized by the male remove the eggs into a waiting fry tank and separate the parents.

The eggs of the Rainbow shark should be kept in well-aerated water and should hatch within approximately a week. They will be free-swimming fry from birth and should be fed on liquid fry food after their yolk sacs are depleted. Any fry that dies should be removed from the aquarium immediately as their corpses may cause ammonia spikes.

Providing the fry aquarium is large enough the Rainbow shark fry should be able to live together without any problems until they reach maturity which happens at about four inches in length. How many fry you will be able to raise to this stage is not known as records of home aquarium breeding all report failure.

Suitable Tank Mates for Rainbow Sharks

We have already covered the aspect that Rainbow sharks do not make good tank mates to other Rainbow sharks unless they are kept in large numbers in aquariums that are too large to be feasible for most homes. They can, however, be kept, and quite happily, with some other species.

Whilst Rainbow sharks make peaceable tank mates to most other tropical freshwater species it is probably best not to keep them with shy types. Potential companions are far better off being calm but strong personality wise. This would include species such as gouramis, barbs, Clown Loach, danios, Plecostomus and rainbow fish.

Species to avoid would be Red tail sharks, Bala sharks, and most other large bottom feeders. They are far too likely to come into contact with the also bottom-dwelling Rainbow shark who will not react well to his territory being encroached upon.

Final Thoughts

Regarded as moderately difficult to keep due to its aquarium requirements and compatibility with other species, the Rainbow shark may seem a little daunting and therefore perhaps not worth the effort. This couldn’t, however, be further from the truth and here is exactly why!

Whilst the Rainbow may not be a true shark in the technical sense of the word it certainly has the personality and the gusto of one. It is fully capable of defending its territory, and will not take any messing with by anything. This makes it a fun and interesting species to watch in your aquarium although one you need to keep from becoming too aggressive which can be easily done.

The Rainbow shark is also beautiful, with its dark sleek body and vibrantly colored fins. They are mesmerizing to watch as they swim speedily across the bottom level of an aquarium and fascinating to see feed. Need I say more? Well, maybe just a little!

Undeniably the Rainbow shark has to be one of the most appealing bottom dwellers in the fish keeping hobby and completely capable of becoming a centerpiece in any aquarium. They are a species that I and others who already own them would highly recommend you keep.

So what are you waiting for? Haven’t you got one already? And if not, why not?