The Rainbow shark is a popular freshwater fish species. They are valued for their unique appearance and resemblance to ocean sharks.
However, we think they might be one of the most misunderstood fish, especially by beginners. They can be difficult to keep so it is important to know what they need if you intend to keep this species. This guide will run through everything you need to know about rainbow sharks, including housing, ideal water parameters, feeding, and breeding techniques.
Let’s dive in.
Recommended Rainbow Shark Care Items:
Rainbow Shark Overview
Rainbow Sharks are part of the Cyprinidae family. They also go by alternate names such as red-finned or ruby shark. Despite their names, Rainbow sharks are not actual sharks. Ocean sharks belong to the Chondrichtheyes family, but rainbow sharks are part of the Cyprinidae family, which is the same family as minnows. So although they share the shark name, their origins are very different. Instead, they got the cool name because they have a shark-like appearance due to their dorsal fin on top.
This species is native to Southeast Asia. They thrive in Southeast Asia, particularly the rivers of Myanmar, Thailand, Laos, and Malaysia. They live in rivers with sandy bottoms and lots of plankton. This species was once abundant, but numbers have dwindled in recent years. Most scientists believe the damming of rivers is responsible for the population decline.
Most rainbow sharks available for purchase in aquarium storms originate from fish farms in Thailand so there is little overlap between the wild and captive cohorts.
Rainbow Shark Appearance
The Rainbow Shark is a dark gray fish with vibrant reddish orange fins.
They have a long, torpedo-like body shape, a pointed snout, and an upright dorsal fin. This upright dorsal fin gives them their shark name as it resembles ocean sharks’ fins.
There is some color variation between males and females. At sexual maturity, males tend to have brighter red or orange fins than females do.
If you’re looking for a unique variation, you could also get an Albino Rainbow Shark. The Albino Rainbow Shark has the same reddish-orange fins of the regular variety. However, its body is white. Everything else about the Albino Rainbow Shark is the same as the baseline variety.
How long do Rainbow Sharks live?
The average lifespan of a rainbow shark is between four and six years long. There are reports of some fish living up to eight years but that is rare.
The quality of water in your tank and general tank conditions are key factors in the length of your rainbow shark’s life. Ideal conditions will keep your rainbow shark at low stress levels, which will help it live longer.
How big do Rainbow Sharks get?
The average rainbow shark size at maturity is about 6 inches long. There are some reports of rainbow sharks reaching lengths of 8 inches, but those are rare reports.
Both normal rainbow sharks and albino varieties reach this length. Males and females also tend to be about the same length.
Rainbow sharks are a fast-growing species. Between two and four weeks of age, the baby fish will have grown to about ½ inch to one-inch in length. From there, it can take several months for them to reach full size.
Rainbow sharks are considered sexually mature when they reach four inches in length.
Rainbow Shark Temperament
Rainbow sharks are territorial fish with aggressive tendencies. For this reason, we don’t recommend other tankmates for rainbow sharks, especially if you’re a beginner.
If you do go the route of other species tankmates, you must look for species that are also semi-aggressive and similarly sized. Some examples of suitable fish include some gouramis, barbs, and danios.
If you fail to add equally-aggressive and similarly sized fish, the larger and more aggressive fish in the tank are likely to seriously harm, if not kill, the weaker fish. Rainbow sharks like to pick on small fish, such as the Chili Rasbora, and bottom-feeders, such as clown plecos or cory catfish.
We also recommend housing at least five rainbow sharks. Your sharks are likely to squabble from time-to-time, so having several ensures that one pair of fish aren’t endlessly fighting. Essentially, the more the merrier within space constraints because it spreads the aggression around.
Rainbow Shark Care
Rainbow sharks do require some sophistication in their care. There are several specifications you’ll want to take into account, around tank size, substrates, filtration, and more.
Overall, they are hardy fish and don’t need excessive support, but that assumes their essential needs are being met.
Stick to these guidelines in order to make sure that your rainbow shark lives a healthy life.
Rainbow Shark Habitat
When planning the habitat of your fish, it is best to mimic their natural environments as much as possible. They live in the rivers of Southeast Asia, with sandy bottoms, lots of plankton, and stray branches and rocks that create natural hiding places.
What is the best tank for a Rainbow Shark?
Although they’re relatively small fish, they require a lot of space. The ideal minimum rainbow shark tank size is 55 gallons. This size is recommended for one fish.
Tank size requirements will increase depending on the number of other fish you keep in your tank. If you want to keep 2-3 rainbow sharks together, like we recommend, then consider 125-gallon tanks. This size gives them each sufficient space to stake out a territory large enough that they won’t feel the need to constantly defend it.
Long aquariums are best for this fish. Horizontal space is key for making them not feel cramped and super territorial. Long aquariums also give you more room for adding in decorations like driftwood and rocks to create more nooks and crannies for privacy.
How many Rainbow Sharks can go in my tank?
The answer to this question depends on the size of the tank. 55-gallons is ideal for one rainbow shark. If you want to keep two or three sharks, 125-gallons is the minimum tank size to consider.
The first step in establishing ideal water conditions for your red-finned shark is to fully cycle the tank. This will ensure your key water parameters, such as ammonia, nitrites, and nitrates, are in-check and able to support your fish. If you add fish without cycling your tank, you will likely kill your fish.
Here are the ideal water conditions for this species:
- pH: 6.5 – 7.5
- Temperature: 72 to 82℉ (77℉ is ideal)
- Water hardness: 5 to 11 DH
Rainbow sharks prefer pH neutral waters between 6.5 and 7.5. Aim for a stable number between this range, as rapid fluctuations in the pH will stress this species. If your pH is too high, check out our pH lowering guide for tips and tricks to get the water in the correct range.
Similar to pH, rainbow sharks do best with consistent temperatures. If your water is consistently 75℉, that is a better situation than constantly trying to increase the temperature to reach 77℉, overshooting it, reaching 82 or 83℉, then trying to bring it back down again. We recommend using an aquarium thermometer to stay on track.
An important additional note for your freshwater fish tanks – when doing water changes, you should never add tap water directly to your fish’s aquarium. Instead, run that water through a dechlorinator – a chemical additive that eliminates chlorine and chloramines.
Lastly, we recommend testing your water weekly with this water kit. Water conditions are an invisible parameter. If they are out of range, the only way you will know is when it is too late and your fish start exhibiting stress symptoms. Better to avoid this situation and stay on top of conditions with weekly testing.
Water Flow for Rainbow Sharks
In their natural environments, rainbow sharks are used to faster moving waters that you would expect to find in a river. To achieve this ideal condition in your tank, you may need more than just an external filter to your tank.
You can also consider a horizontal filtration system in order to keep your water flow high, especially if your fish are in a long tank as recommended.
Here are some additional ideas to increase water flow:
- Adding air stones
- Powerheads – small jets that propel water to increase flow
- Wavemakers to produce waves
- Keeping your tank more open by removing objects like plants and decorations that would otherwise impede flow
If your rainbow sharks aren’t able to swim comfortably, your water flow is likely too fast and strong. To counteract this issue, you can add in decorations like driftwood to break up the flow.
What to put in their tank
Remember – we are trying to mimic their natural environment, so your rainbow sharks will appreciate driftwood and rocks more than bubbling treasure chests and skull heads.
Rainbow sharks prefer sand substrates, as their native waters are rivers with sandy bottoms.
Sand is also a great substrate choice because it’s easy to clean and doesn’t excessively collect food or waste. Fine gravel is also an acceptable choice but you will want to avoid larger chunks of gravel because it can scratch your fish, which predisposes them to infection. Additionally, gravel tends to get dirtier than sand.
If you end up choosing gravel, make sure you clean it regularly in order with a gravel vacuum to maintain water conditions.
Rainbow sharks are used to fast-flowing waters. This means that you can use a strong filtration system which will solve two issues – fast water flow and powerful water cleaning capabilities. Depending on your aquarium set-up and budget, we would recommend either a HOB or canister filter option.
Using both an internal and an external filter in your aquarium is also an excellent way to increase water movement.
When evaluating a filter, make sure you pay attention to the gallons per hour (GPH) rating.The GPH rating determines determines how many gallons of water will be filtered each hour.
Select a filter with a GPH rating that is 4 times the size of your tank. So if you have one rainbow shark in a 50 gallon tank, you will want a filter with a GPH rating of 200.
Decorations and Plants
When you think about decorating your tank, try to re-create a sandy river bottom, complete with rocks and driftwood. The plants and decorations will allow your fish to hide and destress when they want to, and minimize confrontation with other tank inhabitants.
You can use live or fake plants, but live plants are always preferred. They also help maintain your water conditions so it is a win-win for your tank. We recommend durable plant species like the Java Fern or Amazon Swords. If you go the fake route, make sure your plants don’t have sharp edges that could harm your fish.
Rainbow Shark Potential diseases
Important notice: we are not veterinarians at Aquarium Friend so the information below should be used for general awareness only. If you are concerned about the health of your fish, consult a fish health professional immediately.
Rainbow Sharks are generally a hardy species of fish. However, they are not immune to diseases so don’t feel like you can be lax with their tank cleaning or water parameters. Given that they’re freshwater fish, they are most likely to suffer from common ailments like Ich, swim bladder disorder, and skin flukes.
Avoiding illness altogether is your best policy for these fish. Make regular maintenance and water changes a priority.
It’s also important to avoid overfeeding your fish – both for the quality of the nutrients, as well as the water quality. If your shark does get extremely ill, make sure you know about fish euthanization options for a peaceful death.
Rainbow Shark Feeding
Rainbow sharks are omnivorous fish. They’re also mostly bottom feeders. This means that they need a diverse range of foods in order to remain healthy. In the wild, they consume decaying plants, algae, insect larvae, and small bits of meat.
What should you feed a Rainbow Shark?
To replicate their diets in the wild, you can feed them common fish foods, including pellets, flakes and algae wafers. You can also spice up their diet with a few small crustaceans or insects per week, such as brine shrimp, bloodworms, and daphnias.
Because they are mostly bottom feeders, make sure that the foods sink to the bottom of the tank.
Lastly, make sure your Rainbow sharks are getting some vegetables such as sliced or boiled zucchini, boiled peas, and spinach. These are all high in nutrient content and provide good amounts of fiber which assists with digestion.
How often should I feed my Rainbow Shark?
Overfeeding fish is an extremely common issue, which can result in bloat, excess weight gain, sluggishness, and general health issues. For this reason, we recommend starting with one feeding per day and see how your fish reacts. You only want to feed as much food as your fish can easily consume in about two minutes.
If they’re struggling to consume all of the food in the allotted time, you can also split the meal into two servings and feed once in the morning and once in the evening.
Overall, it is better to have slightly hungry fish than overfed fish.
Rainbow Shark Tank Mates
In general, we don’t recommend mixing Rainbow sharks in community tanks. They’re naturally aggressive and territorial, meaning they will get into fights and potentially hurt or kill other fish. However, if you choose to mix your tanks, here are our ideas around the best rainbow shark tank mate choices.
In their natural habitats, rainbow shark dwell near the bottom of rivers. This will be their natural territory in your tank, which means they will also claim caves, hiding spots, rocks, and pieces of driftwood as parts of their territories.
In order to keep the peace, avoid all bottom-dwelling fish, or fish that tend to poke around the bottom, such as catfish, plecos, and Cichlids.
Instead, you will want to pick species that occupy different spaces in the tank, near the middle or top of the aquarium. You will also want fish that have the ability to defend themselves if needed. Here are some potential tank mates are:
If you’re going to mix your rainbow sharks with other fish, we recommend adding all of the other fish to your aquarium first. Introduce your rainbow shark last. This makes it less likely that your rainbow shark will consider the entire aquarium as their territory.
Additionally, plan to create plenty of hiding spaces for your fish. This will help keep stress levels low and give everyone places to escape.
If you’re creating a Rainbow Shark-only tank, we recommend including at least five rainbow sharks. That number disperses the aggression of the dominant rainbow shark so that no one creature is getting picked on more excessively.
Are Rainbow Sharks fin nippers?
Yes, Rainbow Sharks can be fin nippers, especially when living in tanks that are too small. Rainbow sharks are territorial fish and will pick on other bottom-dwelling fish like cichlids and catfish. Long-finned fish, like freshwater angelfish, are also targets. In general, Rainbow sharks should be kept in species-only tanks. If you plan to try to keep them in community tanks, you will want to pick species that occupy different spaces in the tank, like the middle or top of the aquarium.
Rainbow Shark Breeding
Breeding rainbow sharks is difficult because the species doesn’t tolerate one another very well, which makes it difficult to breed. There are very few, if any, documented cases of successful aquarium breeding. Correspondingly, there aren’t many different varieties that you find with easier-to-breed fish; the only alternative type known are albino variants.
If you are planning to defy the odds, these are the minimum requirements for attempting (or else you will likely end up with a dead fish or two):
- 75 gallons is your minimum aquarium size. Go as big as you can.
- Make sure you have plenty of plants and decorations in order to create hiding places.
- Only use dechlorinated water.
- Use an aquarium heater to maintain a consistent temperature between 72 – 82℉.
- Wish on every single lucky star that you have, and then keep wishing.
How to Sex Rainbow Sharks
You can assume that if your fish is less than 4 inches in length, they aren’t sexually mature yet.
Mature female rainbow sharks will have thicker bodies and tend to be darker in color.
The Breeding Process
Once your breeding tank is prepared, add your pair and wait one week to ensure that the couple tolerates one another. If they fight, you may need to introduce a different pair.
To encourage breeding, prime your sharks with plenty of protein-rich foods, like brine shrimp and bloodworms. Perform weekly water changes of about 20-30%.
If your sharks are into the idea, you will begin to see mating behavior, such as rubbing together.
Rainbow Sharks reproduce through egg-laying. The female will lay eggs and the male will then fertilize them by spraying the eggs with his milt. The eggs will hatch roughly within a week. Again, this process is very challenging so don’t be surprised if you never make it past the first stage, where the sharks are too territorial and end up fighting instead of mating.
If you are so lucky and the fish actually breed, you have to consider how to take care of the rainbow shark fry.
Put the try in a separate tank of about 10 gallons of dechlorinated water. You will also need a heater and live plants in this tank too. For the first few days, the fry will feed off of their yolk sacs.
Once the yolk sacs are depleted, feed your fry liquid food for 1-2 weeks before introducing baby brine shrimp.
Your newborns can graduate into your main tank only once they reach 0.5 – 1 inches long. But be careful not to introduce them to the main tank with adults yet, as you will likely end up with fighting fish.
Rainbow Shark FAQs
Are Rainbow Sharks aggressive?
Rainbow sharks are considered semi-aggressive and territorial fish. Semi-aggressive fish are species that can and will attack other fish under the right circumstances. A common triggering situation for Rainbow Sharks is living in a tank that is too small, which makes them feel like their space is threatened.
Within the species, there is a range of aggression levels. Some are naturally more aggressive than others and may become more territorial with age. For this reason, it is recommended to introduce your shark to an established tank when they’re young so they’re less likely to assume the entire tank is their territory.
Will Rainbow Sharks kill other fish?
Yes, Rainbow Sharks will kill other fish, especially if they feel like their territory is being threatened. Ways to reduce conflict in your tank is to only include Rainbow Sharks in large tanks, avoid other bottom dwellers and shark species, and only house with fish that occupy the upper two-thirds of the tank so they have the bottom of the tank to themselves. Due to their territorial nature, these fish are not recommended for beginners.
Can guppies live with Rainbow Sharks?
Generally, we would avoid pairing rainbow sharks and guppies. When Rainbow Sharks are young, small, and less territorial, this tank mate situation could work since guppies and Rainbow Sharks occupy different parts of the tank. However, as the Rainbow Shark gets bigger and more mature, they’e more likely to pick on the guppies, which will stress them out greatly..
Can Rainbow sharks live with tetras?
In a really big tank, you could likely pair tetras with a Rainbow Shark. Bigger, tougher tetras, like Serpaes and black skirt tetras are a little bit tougher than Neons or Embers, and are more likely to be able to deal with a Rainbow Shark as a tank mate. We only recommend experimenting with community tanks for Rainbow sharks if you’re an experienced aquarist.
Can I put a rainbow shark with a goldfish?
No, rainbow sharks and goldfish are not compatible. Goldfish require colder water temperatures than will be comfortable for Rainbow Sharks. Additionally, if your goldfish have long fins, your rainbow sharks will likely try to make a sport out of fin-nipping.
Now that you’ve learned just about all there is to know when it comes to caring for Rainbow Sharks, you should be able to decide for yourself if they’re a good fit for your aquarium.
Rainbow Sharks are beautiful and energetic freshwater fish. However, they’re territorial and semi-aggressive. They’re also famous fin nippers.
If you can accommodate their need for space, occasional chases of community tank members, keep stable water conditions, and have no expectations for breeding them, they make beautiful additions to your large tanks.
What has been your experience with Rainbow Sharks? Do you find the benefits of this species outweigh the territorial nature and semi-aggressive nature?