Image credit: Merlin Senger (CC License)
In the right hands, rainbow sharks are super fun and rewarding pet fish to keep. But in the wrong hands, it can be dangerous. In this care guide, I will tell you all there’s to know on how to care for these majestic fish.
Quick Introduction To Rainbow Sharks
| Name | Rainbow Shark |
| Family | Cyprinidae |
| Species | E. frenatum |
| Origin | Indo-China Basin |
| Maximum Size | 6 inches |
| Care Level | Moderate |
| Temperament | Aggressive |
| Breeding | Egg-layer |
| Diet | Omnivore |
| Minimum Tank Size | 50 gallons |
| Temperature | 24-27 degrees C (75-81 degrees F) |
| pH | 6-8 |
Rainbow sharks are sometimes also known as ruby sharks or red-finned sharks. These fish come from Southeastern Asia – especially the freshwater water bodies of Laos, Malaysia, Thailand, and Myanmar.
First things first, let’s set the record straight. Rainbow sharks aren’t even remotely related to real sharks. They’re more related to carps and minnows than great white sharks! Sorry if I just burst your bubble.
Rainbow sharks come from the Cyprinidae family, while the true great white sharks come from the Chondirichtheyes family.
However, their unique appearance – long and slender bodies, pointed snouts, and erect fins – make them look exactly like miniature sharks!
Rainbow Shark Lifespan
In captivity, the average lifespan of a rainbow shark is between 4-8 years. But they’re also known to easily make it past their 8th birthday under the right care.
These fish enjoy a pretty decent lifespan compared to other popular aquarium fish. For instance, bettas and mollies only live around 2-3 years at max.
That being said, it’s not always ensured that your rainbow shark will lead a long life. If it’s brought up in a poor environment under unfavorable conditions, the fish’s lifespan will naturally be compromised.
Providing a well-rounded diet and a safe and clean environment will go a long way in ensuring your rainbow shark lives its life to the fullest.
At What Age Do Rainbow Sharks Mature?
With fish, there’s no certain age to gauge maturity. Instead, it’s evaluated based on their size. And rainbow sharks reach sexual maturity once they grow around 4 inches long.
Rainbow Shark Appearance
Rainbow sharks aren’t actually related to sharks – I know it’s a bummer! But their slender bodies, erect fins, and pointed snout sure do make them look like tiny sharks.
Rainbow sharks are best known for their beautiful red fins. Put simply, they’re eyecatchers. However, sometimes, the fins take on an orange hue as well. And still, it’s nothing short of outstanding.
These sharks have elongated black, bright blue, or dark blue bodies. I must admit, dark blue coloration is quite rare, though.
Like in great white sharks, the snout is pointed, and the abdominal area is flat. They have two eyes – one on either side. And the head often appears to be sunken.
The body is rounded around the head and tapers off to reach the tail.
They sport a forked tail fin.
The linear area from the eye, gill cover, and mouth has a characteristic brief stripe. And their dorsal fins can consist of up to 11 branched rays.
Males are usually more brightly colored than females and have comparatively petite figures. Females are somewhat darker and larger with a slightly rounded appearance.
Also, a male’s tail fin is adorned with gray lines.
As juveniles, telling the males and females apart is like boiling the ocean. They look pretty much identical.
The subtle dimorphism only becomes apparent as the fish reach maturity.
Rainbow Shark Size
Rainbow sharks aren’t too big, but they sure have a BIG personality. These fish only grow around 4-6 inches (10-15cm) long in captivity.
When first ‘hatched’ from eggs, these sharks are barely any bigger than a microworm. However, under favorable conditions, they will grow rapidly.
For example, between 2 to 4 weeks of age, the fish will probably have grown somewhere in the ½ inch to 1-inch range.
And reportedly reach their full-size potential within the next 1-2 years.
Although there’s not much one can do to unnaturally influence a fish’s growth rate, you sure can encourage the spurt by feeding a nutritious and well-rounded diet, maintaining the water quality, and creating a stress-free environment.
Different Types Of Rainbow Sharks
Albino Rainbow Sharks
Albino rainbow sharks, as you can guess, are a variation of the standard rainbow shark and have a white body instead of the archetypal blue and black markings.
However, the fins and tails are still colored flaming red.
Their body can sometimes take on a yellow or light pink hue as well. A light-colored body contrasted with bright red fins and tails gives these fish a mystical appearance.
And since albinism in these fish is a rare phenomenon, albino rainbow sharks are extraordinaire and, therefore, highly sought after.
Glofish Rainbow Sharks
Glofish sharks are genetically modified rainbow sharks that were first introduced in 2018. These fish were created by inserting the fluorescent gene of different marine organisms like jellyfish into the rainbow shark embryos.
As a result, these fish glow in the dark and blue light.
They come in 4 awesome but patented colors like Sunburst Orange, Electric Green, Cosmic Blue, and Galactic Purple.
Despite the genetic modification, these fish have still retained their iconic red fins and tails.
Other than the colorful and bright disposition, glofish sharks are identical to rainbow sharks in terms of temperament and care they need.
If you’re interested to learn more about these phenomenal fish, you might want to check out this article!
Recommended Readings! Glofish Shark Care Guide
Rainbow Shark Diet
For fish as aggressive as rainbow sharks, one would expect their diet mostly consists of live and meaty foods. However, they primarily snack on algae, zooplankton, and decaying plant matter in the wild. But since they’re omnivores, they’re also known to eat insect larvae, crustaceans, and insects.
I wrote this paragraph about what they eat in the wild so that you make informed decisions on what to feed them in the tank. It’s essential to emulate their natural dietary pattern as much as possible, even in captivity.
This will ensure the fish can have a well-rounded diet that fulfills its nutritional requirements.
Since rainbow sharks are bottom feeders, you need to review and shortlist a couple of different sinking pellet options. Ideally, pellets should make up a good portion of their food intake – a staple diet.
As rainbow sharks have a natural appetite for algae, they’d also benefit from incorporating algae in their diets. You can buy algae in different formats like powder, tablets, and wafers.
You can then fortify the diet with live and frozen worms and insects, as well as blanched veggies once or twice every week.
Here’s a definitive list of all the food you can give your rainbow sharks:
- Sinking pellets
- Algae wafers
- Algae tablets
- Daphnia
- Brine Shrimp
- Bloodworms
- Tubifex
- Blackworms
- Insects
- Insect larvae
- Crickets
- Artemias
- Broccoli (blanched)
- Cucumber (blanched)
- Peas (cooked and skinned)
- Romaine lettuce (blanched)
Here’s a link to sinking pellets by API that I give my bottom-feeders. It’s a brand I fully trust, and my fish, too, seem to love it!
And if you want to treat your little sharks from time to time, there’s no better choice than algae wafers!
I’ll leave a link to Hikari’s Algae Wafers, which are made with pure-cultured spirulina. I’m pretty positive your fish will love it.
Rainbow Shark Temperament
Rainbow sharks are notorious for their temperament, and rightly so. They are so aggressive that 9 out of 10 times, it is advised to keep them alone in a big tank.
However, this anger issue is not seen in the wild. In their natural habitat, these fish are somewhat docile, love to keep to themselves, and seldom prey on smaller fish.
But unfortunately, this temperament doesn’t hold true in captivity.
Therefore, hobbyists strongly recommend against beginners raising rainbow sharks. Things can go south pretty quickly.
Rainbow sharks will claim little territories like decor or rock and guard them fiercely. It won’t think twice before turning violent if an intruder comes nearby.
And that’s the reason you need a considerably large tank that includes plenty of hiding places for these fish.
As juveniles, rainbow fish are somewhat aloof and timid. They usually keep to themselves. However, as they mature, they will begin to assert their dominance by nipping fins, chasing, biting, head-butting, and even tail-butting.
A good part of their aggression can be managed if you provide plenty of space and hiding places. But we still cannot 100% rule out the chances of brawls and injuries.
And by the way, rainbow sharks are bottom-dwellers. So they spend a good amount of time at the bottom of the tank swimming energetically and are most active at nighttime.
Rainbow Shark Tankmates
Given a rainbow shark’s violent demeanor, keeping these fish alone is often advised. Frankly, adding another fish to a rainbow shark tank is like walking on eggshells. But it’s not entirely impossible.
These fish do not tolerate the presence of their own kind or any fish that remotely looks like them. However, they can cohabitate with many qualms with small, mid-water-dwelling, short-finned fish.
Here’s a list of suitable tankmates for your rainbow sharks:
- Gouramis
- Tetras
- Barbs
- Rasboras
- Gouramis
- Rainbowfish
- Loaches (can be dicey)
I skimmed several forums and found that hobbyists have successfully kept rainbow sharks with small schooling species like barbs. That’s probably because barbs look very different from rainbow sharks and swim in the top or mid-level.
While bottom-dwellers make great companions for most aggressive fish owing to their calm temperament and imposing figure, they should not be housed with rainbow sharks.
Why? Because rainbow sharks love to stay at the bottom too. Keeping them alongside any other bottom-dwelling species will give rise to unsolicited stress in the tank and can even prove fatal.
Now, here’s a list of fish that you should never keep with rainbow sharks:
- Other rainbow sharks
- Glofish sharks
- Loaches
- Plecos
- Catfish
- Cichlids
- Red-tail Sharks
- Bala Sharks
Given a rainbow shark’s aggressive nature, there’s always some level of risk involved when adding any new fish to their tank.
Thus, to counteract this problem, you need to first add other fish in the tank and only add the rainbow shark at last. This way, the shark will not perceive the entire aquarium to be its territory.
Also, you need to strategically position plants and decors to create safe hiding spots and break the line of sight to increase the chances of successful cohabitation.
Don’t make the mistake of adding fish like red-tail sharks that somewhat look like rainbow sharks. It’ll end up in a duel and heartbreak for you as one of the fish will be gone.
How Many Rainbow Sharks Can You Keep Together?
Due to their exceptionally angry temperament, the general practice is to keep just one rainbow shark per tank. These fish are even hostile towards other fish that remotely look like them.
If you keep 2 rainbow sharks in the same tank, the alpha will chase, nip and bully the weak one to the brink of death. It’ll be a bloodbath. And no, I’m not exaggerating.
However, if you still insist on raising more than one rainbow shark, the bare minimum number here should be 5. Yes, you read that right!
This way, the dominant fish will have more fish to pick on and bully. There won’t be just one fish on the receiving end of the relentless bullying.
And you’ll need a tank sized 200-gallon or even bigger to comfortably house these many rainbow sharks. Even then, you can’t really rule out the chances of having some fallen soldiers.
How Often And How Much To Feed Rainbow Sharks?
Overfeeding can invite a host of problems – and so will underfeeding. The best practice is to give the rainbow sharks 2 meals per day. Give them an amount they can comfortably eat within 2-3 minutes.
If you plan to give just 1 meal per day, offer an amount they can consume within 5-6 minutes.
But if you find your rainbow shark not finishing all the food you give in one go, you can break it down into smaller meals.
Around 15-20 minutes after the fish is done eating, make a habit to religiously remove the leftover food, so the water quality remains good for a longer period.
Both overfeeding and underfeeding come with their own set of risks.
While the former leads to obesity and a polluted environment, the latter compromises the fish’s development and even lifespan.
Rainbow Shark Water Parameters
- Temperature: 75-81 degrees F (24-27 degrees C)
- pH: 6-8
- Hardness: 5-11
- Ammonia: 0 PPM
- Nitrite: 0 PPM
- Nitrate: Below 20 PPM
- Water Movement: High
- Swimming Level: Low
When raising rainbow sharks, you should always strive to emulate the water conditions of their natural habitat as much as possible. In this section, we will walk you through how to do that step by step.
But first, let’s tick off the basics.
You should have your tank fully cycled before adding your rainbow shark in there. And it’s not exactly a piece of cake. But, don’t worry – it’s not rocket science either.
Properly cycling a tank and ensuring that it has a thriving nitrogen cycle can take several weeks.
I will not go through the nitty-gritty of the nitrogen cycle here in this article, but I strongly suggest you read up on it if you haven’t already.
Right Temperature For Rainbow Sharks
The suitable temperature range for rainbow sharks is 75-81 degrees F (24-27 degrees C). However, experts recommend that you aim to keep it stable at around 77 degrees F.
Remember, the key here is not to chase the ‘right’ temperature. Frequent temperature changes impart more harm than the wrong temperature.
For example, if your temperature continuously fluctuates between 75 and 81 degrees F, it will profusely stress out your fish and compromise its immunity.
Therefore, you mustn’t pinch pennies when buying a heater for your rainbow shark tank.
Right Water Flow For Rainbow Sharks
In their natural habitat in Indochina river basins, rainbow sharks are used to being in high-flow waters. Thus, they prefer strong currents.
To emulate the water flow of their natural habitat, you may need to add more than just one external filter in the tank. While at it, you should also consider adding a horizontal filtration system to keep the water flow high.
There are a couple of other ways to increase the water flow as well. Some of them are:
- Adding air stones
- Keeping the tank relatively open
- Using powerheads
- Using wavemakers
Right pH For Rainbow Sharks
The right pH for rainbow sharks falls somewhere between 6-8. Once again, stability is more important than chasing the right number.
Certain substrate materials and driftwoods are known to change the water’s pH. So, be mindful of that.
Treating Water For Rainbow Sharks
All US tap water and municipal water supplies contain traces of compounds like chlorine, lead, and mercury that are added to kill the harmful microorganisms present in the water.
However, these chemicals are lethal to even the hardiest of fish like rainbow sharks.
For example, when chlorine comes in contact with ammonia, it leads to the production of chloramine, which can be downright fatal for your fish.
Luckily, there’s a solution for it: water conditioners. These chemical additives can effectively eliminate any traces of chlorine and chloramine present in the tank.
Here’s a link to the water conditioner from API that I use for my fish and turtle tanks:
Maintaining Water Quality For Rainbow Sharks
Ammonia and nitrite levels should always be kept at 0 PPM. This is because even the slightest traces of these compounds can have life-impairing consequences on your fish.
And although nitrate levels can be maintained below 20 ppm, it is too potentially detrimental to your rainbow shark’s life.
If the levels of these compounds rise over what’s been stated above, your fish will begin to show signs like panting, red or spots on the body, lesions, frayed appearance, lack of appetite, and so on.
If you don’t nullify these compounds in time, it can swiftly kill your fish.
We suggest checking the water parameters once every week to ensure that everything’s right and nothing evil is brewing in there.
For that, we use and recommend using the API Freshwater Master Test Kit that measures 5 important water parameters: ammonia, nitrite, nitrate, pH, and high pH.
Rainbow Shark Tank Size
Rainbow sharks need a considerably large tank due to their aggressive and territorial demeanor. A single rainbow shark needs at least a 50 to 55-gallon tank.
But as always, the bigger, the better.
I saw some sites (including the GloFish website) mention that these sharks can thrive in tanks sized 20 gallons. But my friend, that’s the farthest from the truth.
These fish love to claim different territories in the tank and defend them aggressively. They’re very serious about it for some reason.
And since these fish spend a majority of their time at the base of the tank, it’s crucial to consider the tank’s dimensions as well.
You should opt for a long and wide tank that offers more space for swimming and other antics than tall tanks with a narrow shape.
Best Substrate For Rainbow Sharks
A rainbow shark’s habitat is lined with sandy bases in the wild. Therefore, they naturally prefer sand for substrate.
Choosing sand serves as an advantage for you as well. It will make the cleaning sessions easier as sand rarely collects or hides food and waste.
But if you’re not a fan of sandy substrates, you can also opt for fine gravel.
Since rainbow sharks spend a majority of their time at the bottom, steer clear of larger and sharper gravel chunks as they can inflict injuries on your fish’s delicate skin and fins.
And that’s not all. Gravel is also notorious for discreetly gathering waste. So, if you choose to gravel, you must stay on top of the cleaning sessions.
I know I portrayed gravel here negatively, but don’t get disheartened. I know many hobbyists who have created and maintained stunning aquariums using gravel.
Plants And Decors For Rainbow Sharks
The best aquarium setup is the one that emulates the natural habitat of the fish. Therefore, your rainbow shark tank should feature several plans and hardscapes like caves, rocks, and driftwoods.
It’s crucial to add plants and decorations to a rainbow shark tank as these fish are highly aggressive and territorial. They will allow subdued fish to hide and minimize potential confrontations between different parties.
That’s not all.
These structures will help establish territories within the tank that they can claim and defend. They’ll also help break the line of sight, which reduces aggressive confrontations.
Whatever plants and decors you choose, first make sure to thoroughly clean them as they may bring along unwanted pathogens with them.
For plants, you can choose between live and fake ones. If you’re using fake plants, make sure they don’t have sharp or protruding edges that can injure your fish.
If I were to give you my two cents, I’d suggest sticking with live plants. They’re not as high-maintenance as they’re deemed to be, look great and natural, and will help keep the tank clean for longer.
Java fern, hornwort, and java moss are some excellent examples.
And lastly, as these fish have a tendency to jump, don’t forget to get a tight and well-fitting lid for the tank.
Recommended Equipment For Rainbow Sharks
Our ethos at Urban Fishkeeping is ‘buy nice or buy twice.’ But that being said, we’re not here to encourage you to burn a hole in your pocket. So instead, we have scoured the internet, reviewed hundreds of reviews, and shortlisted the best – robust yet affordable – equipment for your rainbow sharks.
So, let’s have a look without further ado!
Cascade Canister Filter 1500
What We Love About It:
- Flow valves rotate 360-degrees for easy maneuvering
- Features 5 large-capacity, stackable media baskets
- Easy push-button primer facilitates quick and straightforward prime
- Comes equipped with everything you need to get started
Drawback:
- There were a few complaints about the filter rattling
Hygger Submersible Water Heater
What We Love About It:
- Rapid heating mechanism – warms within 5 seconds
- 3-digit display accurate to 0.1 degrees F
- Heater turns off automatically if water evaporates and heater is exposed
- Intelligent thermostat delivers over-temperature protection
Drawback:
- There were a few complaints about the thermostat
Tetra Whisper Air Pump
What We Love About It:
- Pumps air down to 8-feet deep
- Super quiet operation
- Creates dramatic bubble effect to improve tank’s aesthetics
Drawback:
- There were some complaints about loud noise
How To Breed Rainbow Sharks?
Would you believe it if I said there’s been no documented case of successfully breeding rainbow sharks in an aquarium setting? Owing to their incredible intolerance for each other, getting these fish to breed is next to impossible.
Even professional breeders are known to take the help of certain hormones to encourage these fish to breed.
Nonetheless, I will dish out the standard breeding technique and ways to facilitate the process just in case your sharks ever breed. Never say never!
Sexing Rainbow Sharks
As it is in almost all species in the animal kingdom, males have a brighter appearance than females. Their fins tend to have brighter orange or red coloration.
So naturally, females are somewhat darker than males.
Females also have a slightly bigger body and a rounded appearance than males.
And lastly, thin grayish lines present in a male’s tail fin are absent in females.
If you’re confused, have your sharks sexed by a professional.
Setting Up The Breeding Tank
You’ll need a tank considerably larger than 55-gallon to breed these fish. The bare minimum requirement here would be 75 gallons. But if you can fetch a bigger tank, go for it.
Next, cycle the aquarium and make sure the parameters in the new habitat mimic that of the main tank. As hardy as these fish are, they aren’t really known for their adaptation skills.
Use a dechlorinator to neutralize any harmful components present in the tank. And allocate at least 48 hours to create a clean, safe, and conducive environment.
The temperature should be maintained somewhere between 72-82 degrees F. Ensure the temperature doesn’t shift frequently or suddenly.
Add plants and other aquarium decorations strategically, so they serve as hiding places for the times your sharks lash out at each other. These will also protect the fry later against parents who commit infanticide.
Encouraging Mating And The Mating Ritual
Once the breeding tank is fully prepped, gently net the future parents and transfer them to the new tank. Closely monitor their behavior and temperament towards each other for a couple of days.
If they try to knock the living daylights out of each other, you may have to remove them and choose a new pair altogether.
And by the way, rainbow sharks don’t get pregnant. Instead, they become gravid. A female shark remains gravid for around 1-2 weeks, and you can tell it by her distended appearance around the belly region.
You can pull a few tricks to encourage the sharks to breed.
First, you can feed them protein-rich live or frozen food like bloodworms and brine shrimp.
Second, perform around 25% water change weekly.
And lastly, slightly increase the water temperature by a couple of degrees.
Since there’s no documented case of successfully breeding rainbow sharks as of yet, I didn’t find any reliable information on their mating ritual. It’s like finding a needle in a haystack.
From whatever little I found, it turns out that the rainbow sharks will rub against each other as part of the mating ritual. They may also circle each other in the typical fish fashion.
The female will then proceed to lay hundreds of tiny little eggs – not at once, of course! She will scatter the eggs all over the place. The egg-laying process will go on for a couple of hours.
The eggs are tiny, spherical, and barely any bigger than 1mm. And since they’re adhesive, they’ll stick to different surfaces like the substrate, rocks, decors, and plants.
Once the eggs are laid, the male performs his part – fertilizing the eggs with the milt spray.
Now, the parents have ‘officially’ served their purpose. You can now gently net and place them back in the main tank.
Caring For The Rainbow Shark Fry
The eggs will ‘hatch’ within the next 36-48 hours of fertilization. However, it can take up to 3-4 days in some cases.
Note that the eggs don’t hatch the same way a reptile’s eggs would hatch. Instead, the eggs would morph into different body parts like eyes and tails until the wigglers take their final form.
Now, a 75-gallon tank would be too big for these tiny creatures. They’d find it impossible to find food in a tank that big.
Also, the filter you used for a 75-gallon tank can very well suck in the fry.
Therefore, it’s recommended to set up a 10-gallon tank for the fry.
Leave the base bare – don’t add the substrate – as it will make food hunting difficult for the fry. But you can add plenty of plants that will serve as both shelter and food sources.
Add a sponge filter, tweak the temperature to the right setting, and cycle the tank beforehand.
You can then gently transfer the eggs/fry into the new tank using a nylon net.
For the first couple of days after hatching, the fry will depend on the nutritious yolk sac attached to their body for their nutritional needs.
Once the sac is dried up and absorbed into the body, you must fortify their diet with small foods.
Here’s a quick list of food you can give your rainbow shark fry:
- Infusoria
- Egg yolk paste
- Microworms
- Baby brine shrimp
- Pulverized flake food
Once the fry grow around 1-inch long, they’re big enough to not be confused for food. You can now transfer them to the main tank.
Rainbow Shark Diseases
Rainbow sharks are hardy fish. They seldom contract any disease when kept in the right conditions. However, we still can’t 100% rule out the chances of them getting sick and, unfortunately, dying from it.
They’re just as prone as other freshwater species to specific ailments like parasitic infestations, bacterial infections, fluke, and swim bladder disease.
I’ll touch on some of these ailments in brief below.
Ich
Ich is caused by parasitic protozoan and manifests as tiny white specks across the shark’s body and fins. It’s highly contagious and is even known to transfer to fish without any medium.
At Urban Fishkeeping, we use the Ich-X treatment from Hikari to treat our fish, and it has worked perfectly every time. If you’re planning to use it, strictly adhere to the manufacturer’s guidelines.
Swim Bladder Disease
Swim bladder disease is a condition where a fish’s swim bladder is impacted due to an injury, abnormality, or digestive complications. As a result, the affected fish will have difficulty maintaining its buoyancy and will be forced to swim sideways, sink to the bottom, and float to the top involuntarily.
If the swim bladder disease occurred due to digestive complications, fasting the fish and feeding it fibrous food like peas can alleviate the condition. However, if it’s due to an abnormality or an injury, you will need to consult a vet on the best way forward.
Infections, Infestations, And Flukes
Most kinds of bacterial and fungal infections, parasitic infestations, and flukes can be countered as long as you maintain healthy water parameters and diet. Staying on top of the water changes and feeding a well-rounded diet will prevent these health conditions 9 out of 10 times.
Also, before you add anything new into the tank – be it rock, decor, plant, or fish – make sure to thoroughly clean it first.
Even though rainbow sharks are super hardy fish, to begin with, identifying the disease in its early stages and treating it accordingly will make a huge difference.
Final Words: Rainbow Shark Care Guide
The article was quite long, wasn’t it? It’s almost 5,000 words long! I sure had fun researching and writing this, and I hope it was a good experience on your side too.
Now that you have full knowledge and a better understanding of rainbow sharks, it’s on you to decide if you want to raise these feisty little guys.
While raising rainbow sharks isn’t a walk in the park, it’s not rocket science either. They’re not as high-maintenance as some deem them to be.
Although rainbow sharks demand some extra work compared to fish like guppies and goldfish, rainbow fish offer a beautiful and rewarding experience in the right hands. It’d be a pleasure to raise one. ONE 😉
Recommended Readings!
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