Rainbow Shark: Care Guide, Feeding, Size and Tankmates

Rainbow Sharks, also known as Red Fin Sharks or Ruby Sharks, are small tropical freshwater fish native to Thailand.

They are known for their vibrant red fins and being territorial.

If you’re looking to add some color and attitude to your aquarium this may just be the fish for you.

In this article we will discuss how to care for them, dietary needs, tank mates/compatibility, breeding and much more.

Let’s start with a quick summary before we move on to discuss their appearance and compatibility with other fish.

Want More? Download a free Rainbow Shark guide which will teach you all about caring for this species.

Care Level:Easy/Moderate
Color Form:Gray, Red
Lifespan:5-8 Years
Size:Up to 6″
Minimum Tank Size:50 Gallons
Tank Set-Up:Tropical Freshwater: Rocks, Caves or Plants
Compatibility:Moderate. Get along with many other freshwater fish species

Overview of Rainbow Shark

The Rainbow Shark is a tropical freshwater cyprinid that is somewhat difficult to keep. It would be suitable for fish keepers who have a few years of experience and are looking to expand their aquarium.

They are known for their territorial nature and bright vibrant red fins.

Originating from the warm rivers of Southeast Asia, they were given the affectionate common name of Rainbow Shark, due to their upright dorsal fin which gives them the appearance of a shark.

You should expect your Rainbow Shark to grow up to 6 inches in length and have a lifespan of 5-8 years.

In terms of cost you should be looking to spend no more than $3 per fish, and they are readily available all year round.

If you do intend to keep Rainbow Sharks you should make sure your aquarium has plenty of hiding places for them as this helps to reduce their territorial behavior.

Rainbow Shark

Rainbow Sharks’ Appearance

The Rainbow Shark is a dark gray fish with vibrant red/orange fins.

They have a long, flat stomach with a pointed snout and an upright dorsal fin. It’s this fin which gives them the appearance of a shark.

The Rainbow Shark is a small fish which you should expect to grow up to around 6 inches when fully matured.

It is not possible to identify their gender whilst they are juveniles. You have to wait until they are sexually matured.

Once sexually matured females will have thicker bodies, and males will develop small black lines on the tail fin. Whilst males will be thinner, they will generally have brighter colorations.

A common variety of the Rainbow Shark is the Albino Rainbow Shark.

Whilst the Albino Rainbow Shark maintains the red/orange fins, its body is white. It will grow to a similar size as a traditional Rainbow Shark and matches several of their characteristics including being territorial.

Typical Behavior

The Rainbow Shark is a territorial fish which can cause certain behavioral problems such as aggression and dominance.

This generally happens as they mature. As juveniles they are timid and will spend large periods of their time hiding.

They are active swimmers and tend to spend most of their time dwelling at the bottom of the tank. Due to them being bottom-dwellers, they are known as aquarium cleaners as they will eat the algae growing on the bottom of the tank.

You should make sure your aquarium is long and has plenty of space for your Rainbow Shark to swim on the same level.

Whilst they are peaceful with fish that dwell in higher water, they are known for fighting with bottom dwelling fish, including their own kind.

Such behavior can include biting, chasing and head-and-tail butting.

You can attempt to reduce this behavior by ensuring they are placed in a large aquarium, with a low fish to water ratio. You should also ensure they have lots of hiding places, such as caves, tunnels and other hollowed décor.

Finally, whilst they aren’t renowned for jumping, it isn’t unheard of. For this reason you should make sure your lid is well fitted to prevent them jumping out of your aquarium. Jumping generally occurs when they are first placed in the aquarium.

Habitat and Tank Requirements

As mentioned in the overview section, Rainbow Sharks are tropical freshwater fish that originate from Thailand.

They are active swimmers so adults should not be kept in aquariums smaller than 50 gallons. The aquarium should also have plenty of horizontal space. If the aquarium is too short in length it will encourage them to become more territorial and aggressive.

If you plan on keeping multiple Rainbow Sharks then you should use at least a six foot long, 125 gallon tank (however we don’t recommend keeping more than one Rainbow Shark per aquarium; more on this later).

Due to the Rainbow Shark’s territorial nature, you should ensure your aquarium has lots of hiding places for them. Think caves, treated driftwood and rocks.

Dense vegetation and plants also work. Plants can be used to keep them distracted so it will reduce conflict and also help prevent algae.

As for substrate, they are best suited to sand, as this is what is found in their native Thai rivers. Be careful if you intend to use gravel because the sharp edges can cut them. If you do decide to use gravel make sure it’s very fine.

Finally, you should make sure your aquarium lid is fitted well, they are can jump!

Tank Conditions

You should keep it within the follow parameters: 75°F to 81°F, pH level 6.5-7.5 and a water hardness of 5 to 11 DH.

With Rainbow Sharks you need to keep the pH level stable. Sudden changes in the pH level can cause them to become more aggressive than usual.

Lighting should be kept at a medium level, and the water movement should be moderate.

Rainbow Shark in Aquarium

Compatibility and Tankmates

Let me preface this section by stating if you are looking for a calm community fish, the Rainbow Shark might not be the fish for you.

Whilst they will get along with many other freshwater fish species, they are very territorial and this can be overwhelming for more shy species, such as Marbled hatchet fish and Otocinclus catfish.

As mentioned in the aquarium and habitat section above, they like to take possession of an area of the aquarium; generally the small caves and rocks.

We sympathize with any fish that stumbles upon a Rainbow Shark’s territory! They will be extremely aggressive and chase the intruders away.

Due to their aggression, you need to be careful when choosing tank mates.

As a general rule they aren’t aggressive towards species that don’t look like Rainbow Sharks. As the Rainbow Shark dwells at the bottom of the aquarium, avoid other bottom-dwelling fish such as cichlids and catfish. You should also avoid any similar looking fish, i.e. Red Tail Sharks and Bala Sharks.

When selecting tank mates, look for those fish that dwell in the middle and upper levels of the aquarium.

You also want to pick fish that can defend themselves and have a calm but strong personality. Species such as Gouramis, Barbs, Danios and Rainbowfish are all compatible with Rainbow Sharks.

Finally, a little compatibility trick you can use is: make sure the Rainbow Shark is the last fish placed in your aquarium. This will prevent it trying to claim the entire aquarium as its own and should reduce territory problems.

Keeping Rainbow Sharks with other Rainbow Shark

As a general rule it’s recommended that you only keep one Rainbow Shark in an aquarium at any time. Red Tail Sharks should also be added to this rule.

Like the Royal Gramma, Rainbow Sharks will not tolerate living with its own kind.

In the wild they generally lead a solitary lifestyle and are very territorial. In a normal aquarium there just isn’t enough space and the larger Rainbow Shark will chase the smaller Rainbow Sharks relentlessly until it kills them.

This territorial nature develops with age, so if you get two juvenile Rainbow Sharks they could very well start out getting along, but their relationship will decline rapidly as they mature.

If you insist on keeping more than one Rainbow Shark follow these guidelines:

  • You should keep a group of them (5 or more). This way the dominant Rainbow Shark has multiple fish to chase.
  • Never keep just two Rainbow Sharks.
  • If you intend to introduce more than one Rainbow Shark make sure each has at least a meter of separated territory.

Diet and Feeding Requirements

As mentioned during the overview, Rainbow Sharks are Omnivores which means they eat both plants and meat.

In the wild they generally consume decaying plants, algae, insect larvae and small chunks of meat they find in the river such as Zooplankton.

They aren’t fussy eaters and will consume most things; providing it sinks to the bottom of the tank!

This is good news if you plan to keep Rainbow Sharks in aquariums. They will eat flake food, frozen food, pellets, vegetables and live food with no complaints.

You should aim to keep their diet varied and feed them a variety of food sources, similar to what they would eat in the wild. For instance: algae (tablets or wafers), insect larvae, crustaceans (frozen or live) and zooplankton. To keep their diet varied you can also offer them plenty of vegetables such as spinach, lettuce, zucchini and peas; this will keep their immune system strong.

If you want to make sure their red/orange color is a vibrant shade, regular meals of live and frozen meat should be given to them; frozen bloodworms and brine shrimp will be fine.

This is even more important for juvenile Rainbow Sharks. If you want your juveniles to grow large with vibrant colors, make sure their diet is varied and never overly restricted. Lack of variation can cause stunted growth and poor color expression.

As for their feeding regime, you should aim to spread their food out over 2-3 sessions a day. The total length of feeding time should be around 5 minutes.

If food is left after this time, you are feeding them too much and it will impact your nitrogen cycle.

Rainbow Shark Breeding

In the wild, Rainbow Shark’s tend to mate during October to November, which is when they also reach their sexual maturity. However the exact month can be impacted by changing seasons, and depends on the length of the day and temperature.

Note: You can assume that if the fish is less than 4 inches in length, they aren’t sexually mature yet.

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. From here the eggs will hatch within the week.

Unfortunately though, breeding Rainbow Sharks in an aquarium is extremely challenging and we are yet to hear of any success stories.

Again, this is more than likely because of their aggressive and territorial nature in confined settings.

The majority of Rainbow Sharks you find available for purchase will be bred in commercial farms based in Southeast Asia.

Is the Rainbow Shark Right For Your Aquarium? (Summary)

The Rainbow Shark would make a great addition to your community providing they aren’t kept with the same, or similar looking fish.

Whilst they are known for being territorial, providing you give them a suitable aquarium environment and match them with the appropriate tank mate(s), you shouldn’t have too many problems with them.

They are a beautiful fish and an active swimmer, so will provide you with enjoyment when watching them in an aquarium.

They are good eaters and will eat a variety of food forms including pellets, flakes and frozen meat.

If you are planning to keep Rainbow Sharks, you should also make sure that you’ve got some fishkeeping experience already, as these fish generally aren’t for beginners.

Do you keep Rainbow Sharks? Let us know in the comments section below…

About Robert 255 Articles
Robert Woods is the creator of FishKeeping World, a third generation fish keeper and a graduate in animal welfare and behavior. He is also a proud member of the Association of Zoos and Aquariums, the Marine Aquarium Societies of North America and the Nature Conservancy.


  1. Hi i have a rainbow shark and an albino who have been doing a mating dance for hours never done this before,awesome to watch

  2. HI, I have a rainbow shark and he is now coming up to 14 years old. He shows no sign of slowing down and is still very active. We love him.

  3. Hey I just got 2 rainbow sharks 1 normal and one albino which I call custed I didn’t have much room to buy a big tank so I got a 2 foot which I think is 15 gallons in the tank I also have a ghost knife a upside down catfish and a pepper mint bristle nose I also have 2 silver shark and a 80 gallon tank which have a variety of other fish I have noticed my albino rainbow shark chasing my other rainbow shark and my 2 silver sharks nut won’t chase anything else away is there anything I can do with the tank he’s it to get him to calm down?

    • Do you turn your lights off any make sure they have plenty of down time? Do you also have plenty of hiding places for your fish? Failing this, you could use a tank divider. Robert

  4. I think my sharks have laid eggs.. but I can’t find any pictures to confirm it.. any suggestions on how to find out what they look like?

  5. I’ve had a rainbow shark for about 4 years, who lives alone, I want to Add something to the tank with him that is compatible, any suggestions?

  6. Hi. I just bought 2 rainbow sharks & 2 bala sharks along with 2 sucker fish. They didn’t tell me about any of this. I thought if they come from the same tank then they should be okay but now I’m noticing that 1 of my rainbow sharks are chasing all the other fish in the tank. I’m sure I know the answer but (can I put my rainbow shark in with my beta as that’s the only other tank I have with heat.? If not my next question is (what’s the ideal tank for both species of sharks.? Sand, tank temp, tank size, tank mates etc.?)

    • I’d advise keeping the Rainbow Sharks and Bala Sharks in different tanks. All the information on tank conditions are listed here in this article for rainbow sharks. Bala Sharks prefer to be kept in schools of at least 6, they are also prone to becoming stressed very easily, so it won’t help their case living with the Rainbow Sharks. Thanks, Robert

  7. I have a 4ft tank that I have managed to cohabit 2 Reeves turtle’s 2 leopard guppies 4 platies and 1 rainbow shark I’m also just about to add a gold nugget pleco so far no fatalities

  8. We just got our son 5 shark fish, 2 rainbow sharks, 2 silver and black sharks and an albino shark. The second to third day the two rainbow ones began their territorial aggression but have since become more laid back. I have noticed that our albino tends to stay to itself. Do we need to add another albino to our tank or is it fine being a “loner”?

    • Hi Leah, firstly, we only recommend keeping one rainbow shark per tank. As you’ve noticed they can be aggresive towards one another. When you say silver and black shark, do you mean the Bala Shark? Again, we don’t recommend keeping these in the same tank, they’re also aggressive and need much larger tanks(around 150 gallons) You can read more about them here: https://www.fishkeepingworld.com/bala-shark/ Rather than add more sharks, I recommend that you split them up into different tanks. Thanks, Robert

  9. I have a juvenile rainbow shark in a community tank. He has been in there about two weeks . It is 36 gallon tank. Every time I feed the fish he goes bonkers and chases everybody and makes it hard for them to eat. I have three Coreys that he doesn’t bother at all. What can I do?

    • Hi Richard, unfortunately this is the nature of Rainbow Sharks. They are extremely territorial. Provide your other fish with plenty of rocks and plants to hide in to help him calm down before feeding time. You might want to consider feeding him on his own at one side, them feeding the other fish while he is distracted. Failing this, you could use a divider at feeding time, all through this will be a pain! Eventually you’ll also need a larger tank. Thanks, Robert

    • They require different water temperatures so they can’t be kept together for that reason. Thanks, Robert

  10. Hi I recently got a rainbow shark two days ago (thinking I got a red-tailed shark) and just found out today. I noticed that there isn’t really any big differences, but I’m really wondering to how fast they will grow to they’re mature size because he is still a juvenile, but I have him in a 10 gallon tank. How long can he last in there until I get a bigger tank?

  11. I have a baby albino rainbow shark in a 30 gallon tank with 2 Molly a silver dollar and an Australian rainbow fish. Do You have any advice on how to raise him?

  12. Hey
    So my rainbow shark is not aggressive at all. Actually is the most docile fish in my tank. Could that be from luck; or from the order my fish have been added to my tank??
    My roommate just surprised me with 2 new mollies and my rainbow shark seems to have instantly made best buds with them. The Trio literally go everywhere And do everything together. Even share the same hiding spot. Is this odd? Or something I should keep my eye on? I have multiple tanks so moving the mollies won’t be an issue if needed.
    Tank size :80 gallons.
    Community: 4 angelfish (4years in tank),1 Kribensis Cichlid (2 years in tank) 1 Rainbow shark(7 months in tank) and the 2 brand new mollies (2 weeks in tank).

    • Hi Jade, it definitely sounds like just good luck! Keep at eye on them as they grown and separate if you see any signs of aggression. Thanks, Robert

  13. I got a rainbow shark he is fairly very active. He acclimated well presenting little to no stress. He’s in a 30 gallon tank and has started kicking up sand. I was wondering if this is normal?

    • Hi Courtney, is he rubbing himself on the sand or just flicking it around? I’d say if he is rubbing himself on it he might have some sort of infection. If he seems otherwise happy though, just keep an eye on this behavior. Thanks, Robert

  14. Hi Robert, love the article. I have a 65 gallon tank with about 11 fish. The rainbow shark only chases the tri-color shark which is much bigger than him and mostly at feeding time. I assume it is the same reason as why they chase the bala sharks? The two species (bala and tri-color) are very close in appearance. Probably going to move one of them out, just wondering if this is something you see normally?

  15. So my daughter was gifted a 4 gallon tank and an albino rainbow fish for her birthday. Now I see this is way too small- was approved by the pet store and they trusted that info. So he’s been living here for two weeks he mostly hides, what can I do? Should I take him back to the pet store? I’m not sure I’m up for keeping a 50 gallon tank.

    • Hi Regan, unfortunately most pet store employees simply aren’t trained well enough to understand the care needs of each species. A 4 gallon tank is too small for any fish let alone a fish of this size. If you aren’t able to buy a larger tank, I would return the fish to the store. Thanks, Robert

  16. I have one rainbow shark along with 3 guppies, one molly, 2 skirted tetras and one red eyed tetra. The shark is about 3 inches long and for the last 3 days has stayed continuously behind thew filter, hanging upside down. I’ve had it for about 5 weeks. Is this hiding normal, and should I be concerned? The tank is a 40 gallon.

    • Hi Jeffrey, do you have plenty of other hiding places for him? These fish are quite territorial and need their own territories. Juveniles are usually very timid and like to hide away so the behavior is quite normal. Thanks, Robert

    • Hi Nila, please take a read through this article for guidance. You should only keep one of these fish per tank. Thanks, Robert

    • Hi Nila, it could have swim bladder disease, if after research you think this sounds likely, you can increase the tank temperature and fast him for three days. You should only house one of these fish per tank. Thanks, Robert

  17. I’ve recently got 5 rainbows, 3 normal and 2 albino. All are quite large. I can tell that I have 1 male and 2 female with the normal, but how do you tell the sex of the albinos? I’m guessing they don’t get black stripes on their fins!

    • Hi Amanda, females tend to be larger and more round than the males. Also ensure that you have a large enough tank for a group of this size (minimum 125 gallons). Many thanks, Robert

  18. Hi, I love this fish & want them in my 3 ft tank it has driftwoods in it but currently i own 6″ tiger oscar. I want to know will they live with oscar?

    • Hi Vivek, it really depends on the individual behavior of the fish. I would recommend housing them together with caution. Some can get on fine, whereas others will be aggressive towards each other. Thanks, Robert

  19. Anyone ever keep keep a rainbow in an out door pond in SoCal? I want him to have more swimming space. But the pond is not heated. He is about 4 years old now in my 30gal.

  20. Hi can rainbow sharks live past 8 years old? I have a male who is coming up on 8 years old he’s about 5 1/2 inches and I’ve become quite attached to him just wondering how much longer I might have with him?

  21. Hi my name is Dean,
    I recently acquired three rainbow sharks, one silver shark, and fifteen tiger barbs, and put them in a 55 gallon aquarium. The tank has no substrate, several rock caves that are open, other rocks, and mussel shells. The fish are not large, and now I have read your articles.

    The fish are interesting, I like watching them, and they like watching me. Although, the rainbow sharks have started hiding more, except at feeding time. I am hoping for the best. I belong to a fish club and suppose I may have to pull somebody out if they get too rough. I’m telling them to get along, and spending time with them seams to help.

    Thank you for sharing information!
    – Dean

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