The Complete Rainbow Shark Care Guide 2021: Size, Tank Mates, Feeding and Breeding

The Rainbow Shark isn’t related to the shark family, but it can be a great addition to a fish keeper’s tank.

They earn their shark name because of the shape of their body. They sport a long, green or black body, and a flat abdomen. Their mouths hang at the bottom of their faces and they have fins and large eyes. All these features are commonly associated with the shark family.

They’ll catch the attention of anyone passing by. Their red fins are vibrant and contrast well against the bottom of many tanks.

While they’re beautiful to look at, they can be a bit tricky to keep in your tank.

Rainbow Shark Care Guide

The Rainbow Shark is perfect for those who are relatively new to fish keeping. Even if this will be your first species in your tank, they can be easily cared for with the right information.

Their semi-aggressive temperament and tank requirements can be a bit more demanding than other beginner fish. However, if you’re willing to put in the time and effort to effectively take care of your Rainbow Shark, owning one can be a breeze.

Don’t let the downsides ruin the thought of owning a Rainbow Shark, they can be a great addition to a tank and are a beautiful fish to have around. It can bring a lot of life and color to a tropical-themed tank.

Rainbow Shark Behavior

Rainbow Sharks can be a notoriously difficult fish to keep in line for beginner fish keepers.

This is because they can be highly territorial and aggressive.

If you have other fish such as Guppies, Betas, or Mollies, be on the lookout. The Rainbow Shark will often chase around and harass these friendlier fish who won’t strike back at them. They’re also known to be aggressive with other fish who can be equally aggressive.

Because of this, It’s important to provide the ideal tank setup for a Rainbow Shark so it won’t feel compelled to constantly defend its territory.

If you do plan on inviting your Rainbow Shark into a community tank, you should be warned that it won’t play well with others if there are too many fish.

Even if you place the Rainbow Shark in a larger tank (above 50 gallons), it can be a difficult fish to handle if more than three or four other fish is sharing its space.

The fish won’t display many of these aggressive behaviors at first. When they’re younger and in their juvenile phase, they’ll often be timid and shy. You’ll find in the corners of your tank or underneath structures for the most part. They’ll continue to hide until they feel confident enough to become a predator as an adult.

It should be noted that this fish isn’t known for jumping out of the tank, but the behavior has been noted from them when initially being placed in a tank. Because of this, you must have a lid on the top of your tank, especially when first introducing the Rainbow Shark to its new home.

As an adult, most of their time will be spent on the bottom of your tank. They enjoy feeding on the algae that are naturally produced at the bottom of your tank or along surfaces such as driftwood or grave.

Because they spend much of their on the bottom, they’ll be most aggressive to other fish that live in the same area. If you’re going to put the Rainbow Shark in the same tank as other fish, it’s a good idea to pair it with fish that will spend most of their time toward the top of the water column.


The Rainbow Shark looks like how you would imagine, like a shark. Besides the fact that they’re not in the shark family, the main difference is the size of the Rainbow Shark.

For having ‘shark’ in its name, it doesn’t grow nearly as large as sharks. You can expect the Rainbow Shark to grow to a maximum of six inches. If you have one of these in your tank, don’t expect it o take an overwhelmingly large amount of space.

Their bodies will be elongated and have a dark-greenish color to it. On the underside, the fish has an equally long stomach that is both flat and long.

Their snouts will be pointed and their mouthers will be on the lower half of it. Their large eyeballs will gleam in the water and give it the appearance of the predator of the sea.

Interestingly, their mouths also house two antenna-like whiskers. They protrude from the front and are used by the Rainbow Shark to help detect its surroundings and feed more effectively on the bottom of your tank.

They also have an upright dorsal fin. This fin, fins on the underside and their tail are all typically colored in a vibrant, dark red.

All of these features combine to help the Rainbow Shark truly look like the beasts we all know that call the sea they’re home.

Differences Between Male and Female

The Rainbow Shark has a couple of different key distinctions between males and females. You should be able to tell their genders apart with relative ease.

Males will have a body that is significantly thinner than their female counterparts. Their beautiful, red dorsal fins will also be beaded with thin and black stripes.

These features should be easily spotted from outside of the tank, you shouldn’t need to pull them out to tell the key differences.

Tank Setup

The Rainbow Shark hails from the tropical freshwaters of Thailand. Because of its origins, you’ll want to do your best to imitate the same habitats that they would find in the wild.

They do the best when their substrate consists of sand, similar to the waters of their homeland. Their fins aren’t well protected, so using gravel is ideal for keeping their bodies in top condition.

If you intend to use gravel, be wary that the sharp edges of the rock can damage their fins. However, gravel can be a great attractor for algae to constantly feed your Rainbow Shark or other bottom feeders.

The Rainbow Shark is an extremely active fish. It’ll constantly be zipping across your tank, bumping into other fish and structures alike. This can bring a lively atmosphere to your tank and keep it consistently interesting to the eye. Because of this, it’s recommended to use a tank of at least 50 gallons. Any less and you’ll be depriving the Rainbow Shark of a healthy environment.

Their frequent movement also calls or a long, horizontally-shaped tank. Ensure that your tank has plenty of widths so the Rainbow Shark can freely move where it pleases.

If you’re worried about the aggression toward other fish, a possible solution may fill your tank with dense vegetation or many plants. Having increased vegetation will distract the Rainbow Shark and keep it busy feeding instead of constantly bumping into other fish in the tank. This can also help reduce the number of algae in your tank!

On top of this, the decreased space will allow for less room for the Rainbow Shark to make its home. This can quickly cause territorial issues with other fish who feel like their home is being invaded by the Rainbow Shark or vice versa.

If you’re planning on having more than one Rainbow Shark, you’ll need at least a 120-gallon aquarium that’s at least six feet wide to provide plenty of space for both Rainbow Sharks.

However, it’s not recommended to keep more than one in your tank at a time. They don’t play with others and that means they don’t play well with those of the same species. Because they’ll be so territorial and have a habit of disturbing other fish, you can quickly create a feud between the two.

There should also be plenty of structure and cover throughout the tank to decrease aggression from the Rainbow Shark. It’s territorial and won’t like its space being intruded upon. By having multiple structures, caves, and cover for the Rainbow Shark to live within, you’ll allow it and other fish to have more options in terms of the space they occupy.

How to Care

The Rainbow Shark doesn’t require extravagant conditions to be met within the tank, but there is important information you should note.

The temperature should be kept between 75 and 81 degrees Fahrenheit, and a water hardness of between five and 11 DH for optimal health.

If other fish in your tank requires a large amount of oxygen or aeration, the fish may not be the most appropriate choice. They’ll need a stable and moderate amount of water movement. If you’re trying to replicate a river or stream’s level of oxygenation in your tank, it may be too much for the Rainbow Shark.

It’s important to note that the pH level must be kept relatively stable, even within the 6.5 and 7.5 range. If a sudden change happens to pH levels, in either direction, it will cause the Rainbow Shark to become irritated and increasingly aggravated. This will cause them to become more aggressive than usual and will cause you a giant headache.

Lighting should be kept at a moderate level, although the Rainbow Shark isn’t too picky when it comes to lighting.

Ideal Tank Mates for a Rainbow Shark

The Rainbow Shark is a semi-aggressive fish, but that doesn’t mean it won’t get along well with other types of freshwater fish species.

You’ll have to be a bit picky when choosing a tank mate, but it’s not impossible. Look for species of fish that will spend most of their time in the upper water column of your tank. That way, your Rainbow Shark and other fish won’t interact as much with each other. This separation is key when considering a tank mate.

In the same vein, don’t consider fish that dwell on the bottom of the tank. This could be the Siamese Algae Eater, catfish, or cichlids. These are all species of fish that will spend most of their time on the bottom of the tank and thus be a problem for the Rainbow Shark.

Appropriate fish will be able to hold their own against the Rainbow Shark. If they can adequately defend themselves in the face of aggression, they’ll receive less attention from your Rainbow Shark.

This mutual respect will bring peace to your tank and can be an effective strategy for creating a small community for your Rainbow Shark.

Rainbowfish, Barbs, and Gouramis are all appropriate fish that will co-habitat well with a Rainbow Shark.

Once these other fish have established their territory, the Rainbow Shark will be much less likely to claim its territory over a large portion of the tank. You’ll have less trouble with its aggression issues.

Pro Tip: The Rainbow Shark will try to claim its space immediately. Because of this, it can be helpful to place the Rainbow Shark in your tank last out of all your fish.

Multiple Rainbow Sharks in a Tank

In general, keeping these aquarium fish  with others of its kind is a bad idea for a fish keeper.

When found in the wild, Rainbow Sharks will be loners and not interact with any other fish. This includes its kind.

If you’ll be keeping multiple Rainbow Sharks, be prepared for continuous brawls. The larger of the Rainbow Sharks will typically overcome the other and claim its space.

This is because of their above-average movement throughout the tank. An average fish keeper simply won’t have a large enough space within their tank to be able to comfortably accommodate more than one Rainbow Shark.

If you find that you will be able to have a large enough tank, some helpful tips can guide you along your way:

  • If you keep more than one, keep a lot. By having a large group of them, the largest of all the Rainbow Sharks will be constantly dealing with multiple fish. This will create less overall stress on an individual Rainbow Shark.
  • Keeping two Rainbow Sharks will almost certainly lead to the death of one. Their attention will be undivided for a large majority of their time and you’ll soon find that you’re back to one Rainbow Shark.
  • The horizontal length of your tank is just as important as the amount of water it can hold. A tank with more than one Rainbow Fish should be at last 120-gallons large and at least six feet wide to provide enough space for the group of them.

What To Feed Them

Rainbow Sharks aren’t picky eaters.

They’ll consume most materials and debris that find their way to the bottom of the tank. If you find that this isn’t enough algae and other food substances, you can simply feed them traditional fish food.

This includes:

  • Pellets
  • Vegetables
  • Live food
  • Flake food

You should keep their diet varied for the best health. If you fail to provide a varied diet, their growth and development may become stunted and they won’t grow to their true size. Try switching up the food it eats every few days or after a week. Keep a rotation for them.

Some examples of food include traditional vegetables, insect larvae, brine shrimp and frozen bloodworms.

You’ll be able to tell that your Rainbow Shark is eating will by their coloration. The shading should be vibrant and beautiful.

Spread their feeding times throughout the day. A full day’s worth of food should be given out in at least two sessions if not three.


Breeding Rainbow Sharks within an aquarium setting is extremely difficult. Success isn’t often found outside of commercial purposes.

This is likely because of natural events that occur in the fall. In the wild, the Rainbow Shark will mate during October and November. The actual spawning season is triggered by falling temperatures and water conditions, which are incredibly difficult to replicate in an aquarium setting.

Is A Rainbow Shark Suitable For Your Aquarium?

Overall, the Rainbow Shark is a beautiful and exciting fish to have dwell in your tank.

However, they come with their own set of issues and can quickly become a problem fish if you’re not knowledgeable enough to provide a peaceful habitat.

If you’re considering owning a Rainbow Shark, ensure you can properly provide for it or you’ll be doing a disservice to its tankmates as well as the Rainbow Shark itself.

If you’re a beginner, it’s okay. You’ve done the first step of researching the fish, you simply must be careful in your planning to provide a good habitat for your Rainbow Shark.

Plus, they help clean the algae in your tank for you. What’s not to love about that?

Richard Rowlands
Richard Rowlands

Hello fellow aquatics enthusiasts! My name is Richard Rowlands. I’m an aquarium keeper and enthusiast and have been for about 25 years or so. While I won’t claim to be the end-all expert on aquatic life, I will say that I know my way around a tank.

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