A bottom dweller with a vibrant coloration, the Rainbow Shark is an excellent choice for any aquarium. Offering quirky behavior and a gorgeous display of both attitude and color, this fish is a good option if you are in the market for a new fish species.
It can be intimidating to add any new fish to your aquarium, but with a little bit of knowledge of the fish’s basic behaviors and tank requirements, you’ll be on your way to becoming a Rainbow Shark owner in no time. Consider our ultimate guide to the Rainbow Shark, and get to the aquarium store today.
A tropical freshwater fish species, the Rainbow Shark is native to Thailand. Not a Shark but instead a large fish, this cyprinid can be a bit difficult to keep for inexperienced aquarium hobbyists. It is ideal for fish keepers with several years of experience who are looking to build their aquariums to larger sizes.
Rainbow Sharks are found in the wild in the warmer rivers of Southeast Asia. They were given their name because of their upright dorsal fin, which makes them look somewhat like a Shark as they are swimming through the water.
Rainbow Sharks are a good idea for more experienced fish keepers who are looking for a long-term fishkeeping investment. These fish live for up to eight years in captivity, providing companionship for quite some time. An affordable option among its peers, the Rainbow Shark costs only about $3 per fish.
Rainbow Shark Appearance and Behavior
Rainbow Sharks are known for aggressive, territorial behavior, as well as for their distinctive appearance. These fish generally grow up to six inches in length, although some may be significantly larger or smaller.
Rainbow Sharks tend to be dark gray to black in color, with bright red or orange fins. They have long, flattened stomachs with pointed snouts and upright dorsal fins, the latter of which is what gives them the appearance of a Shark. These fish are small even when fully matured, and it can be difficult to tell the difference between the sexes.
It is impossible to determine gender when your fish are juveniles, but once they have matured, there are several subtle signs you can look for. For starters, females have thicker bodies, while males will have small black lines on their tail fins. Males are thin but also have brighter colorations, which are used to attract female attention during the mating process.
There are several variations of the generic Rainbow Shark, with the Albino Rainbow Shark being one of the most unique and popular. The Albino Rainbow Shark still has reddish orange fins, but instead of a black body, it is instead white. These fish grow and behave in the exact same way as the traditional Rainbow Shark, but will continue to be pale in color throughout their lives.
Rainbow Sharks are incredibly territorial, which can cause some problems if you are keeping them in a community tank. They can become aggressive and engage in violent shows of dominance against fish of other species as well as toward other Rainbow Sharks. These behaviors are more common as the fish begin to mature – as juveniles, the fish will spend most of their day hiding from other fish.
When they aren’t fighting, Rainbow Sharks are active swimmers and will spend most of their day at the bottom of the tank. They do eat small amounts of algae from the substrate, making them a good option if you are looking for a new or a supplementary algae cleaner for your tank.
Rainbow Sharks will ignore fish in other levels of the water column, but they will become aggressive toward fish that swim on the bottom with them. Therefore, you should invest in an aquarium tank that is both long and has plenty of space for your Rainbow Shark at the lower levels. They will fight with any fish that gravitate toward the bottom of the tank -even other Rainbow Sharks.
When Rainbow Sharks are angered or feel threatened, they will react in a variety of ways. You might spot your Rainbow Shark going after other fish to bite them, chase them, or butt their heads and tails. Keeping your fish in a tank that has a low fish-to-water ratio can help reduce these behaviors, as can providing plenty of hiding spaces like caves and tunnels.
Rainbow Sharks also occasionally jump. Therefore, you must make sure your lid is tightly fitted so that they cannot jump out of your aquarium. This is most common when your Rainbow Sharks are first housed in their new environment, but can occur at any time. Make sure you are vigilant about monitoring your Rainbow Sharks for any signs of injury that may have been brought on by trying to jump out of the tank and potentially colliding with the sides or top.
Rainbow Shark Tank And Water Requirements
Because Rainbow Sharks are tropic fish native to Thailand, they need aquariums that are both large and warm. As active swimmers, Rainbow Sharks should not be kept in aquariums that are smaller than 50 gallons. Horizontal space is more important than vertical dimensions, because these fish need lots of bottom space in which to swim.
If you purchase a smaller tank, your fish could become aggressive. If you plan on keeping multiple Rainbow Sharks, make sure you have a tank that is at least six feet long and 125 gallons in size. Your aquarium should be kept warm, at temperatures between 75 and 81 degrees Fahrenheit. The ideal pH is 6.5 to 7.5, while water hardness should be between 5 and 11 DH.
While Rainbow Sharks can tolerate wild fluctuations in temperature, they cannot handle wild swings in pH. Keep your pH levels stable to ensure the optimal health of your Rainbow Sharks, and remember that sudden changes in pH can cause your fish to become hostile and aggressive.
Use minimal to moderate lighting in your tank. The same ratio applies for water movement – you don’t’ want to overdo it with either of these parameters, but you also need to provide your fish with ample flow and lighting to keep them healthy and to mimic their natural environment.
You will also need to add a heater and a filter to go with your tank. Make sure the filter you select is designed to work with a tank your size, and consider using a tank stand. This will be strong enough to hold a larger tank. You should try not to use an under-gravel filter, as it will not be compatible with sand or other lighter substrate materials.
When you fill your tank, let the water sit for two weeks before introducing fish. This will give the water plenty of time to cycle and allow the chemical composition of the water to stabilize. Keeping your tank far away from windows and vents can prevent the temperature from fluctuating too much, which can be detrimental to tropical species like the Rainbow Shark.
Decorating A Rainbow Shark Tank
Due to the territorial and aggressive nature of a Rainbow Shark, your tank should have plenty of hiding places. Consider adding structures like caves, driftwood, and rocks to your tank. Rainbow Sharks will not eat your plants, so you can also add densely planted vegetation and other live plants. Plants will help filter your water and reduce algal buildup, and will also distract your Rainbow Sharks by providing them with a place to hide.
Consider a light substrate for your Rainbow Shark’s tank. In the wild, these fish are adapted to sandy river bottoms, so that will be your best choice. You can also use gravel, but if you do, be careful – the sharp edges of the gravel can easily cut your fish and cause injury. Therefore, you should only use gravel that is very fine.
Again, make sure your aquarium lid is well-fitted to prevent injuries deaths related to jumping.
What Do Rainbow Sharks Eat?
Rainbow Sharks are opportunistic omnivores, eating both plants and meat that come their way. In the wild, they prefer to eat items they find in the river, such as decaying plants, algae, insect larvae, and other small chunks of meat. Zooplankton are another popular food choice.
Rainbow Sharks are not picky when it comes to their food, and will happily eat anything they can find, as long as it sinks to the bottom of the tank. If you keep a Rainbow Shark, you can feed it just about anything you are feeding its tank mates. They will eat vegetables, live food, frozen food, flake food, and pellets with nary a complaint.
Whatever you do, try to keep their diet varied and feed a variety of food sources similar to what they would find and choose to eat in the wild. You can feed algae tablets or wafers or frozen or live crustaceans. Zooplankton can also be fed, as can insect larvae. If you really want to shake things up, you can even feed them vegetables like spinach, lettuce, peas, and zucchini. This will add fiber to prevent constipation and also keep their immune systems strong.
Providing a varied diet is especially important for juvenile Rainbow Sharks. Young Rainbow Sharks need diverse sources of food so that they can grow large and colorful. If you fail to provide a varied diet, your juvenile fish will have stunted growth and not express color to the best of their capabilities.
Feed your fish two to three times a day – more often is preferred to a large feeding just once a day. Feed them only about as much as they can eat within five minutes. Anything more than that can result in overfeeding, and if it doesn’t, the leftover food can contaminate your tank and impact your nitrogen cycle.
Rainbow Shark Tank Mates
If you are looking for a peaceful, easygoing fish that will get along with all of your other tank mates, the Rainbow Shark is definitely not the fish for you. These fish can get along with many other freshwater fish species, but they are by nature extremely territorial and this can be overwhelming, if not dangerous, for shier, less confrontational fish species.
Rainbow Sharks have a tendency to express dominance and territoriality over a certain area of the tank. They will claim a section of the aquarium as their own, and not leave it alone. This is most commonly done with caves and rocks, where they will defend their turf against all fish who come near it.
Be very careful when choosing tank mates, as you want to choose a fish that does not closely resemble the Rainbow Shark and also does not live in the same area of the water column. You should avoid fish that look similar to the Rainbow Shark, such as the red tail shark and bala shark, as these will become frequent targets of your Rainbow Shark’s aggression.
Other bottom-dwelling fish you should avoid are cichlids and catfish. You can get away with keeping any fish that hang out toward the top or center of the water column, such as barbs, danios, gouramis, and Rainbowfish.
To help ensure compatibility, make sure the Rainbow Shark is the last fish placed in your aquarium. This will make him less likely to try to claim certain sections of the tank as “his own,” and will reduce territorial behaviors as a whole.
You should also try to reduce the overall number of Rainbow Sharks you have in a single aquarium at a time. Like many other spices, including red tail Sharks and royal grammas, Rainbow Sharks do not like living with their own kind.
In the wild, Rainbow Sharks are solitary and will stay far away from other creatures. The same rule applies within your aquarium, but tenfold, as your Rainbow Shark will not have enough space to roam and the larger Rainbow Shark will chase the smaller ones relentlessly until they eventually die.
These behaviors worsen with age, so don’t think that time will help heal the relationship issues between your fish. Juvenile Rainbow Sharks may start off on the right foot, but their relationship will quickly decline as they age.
In your tank, you will likely notice your Rainbow Sharks preferring to hang out in one or two favored spots. This is not a cause for alarm unless it’s clear that one Rainbow Shark in particular is being bullied by the others. Some Rainbow Sharks are more nocturnal than others, preferring to leave their hiding places and swim around after dark, but others may be too terrified to leave their cave or den due to the aggressive behaviors of other fish.
That being said, if you want to keep multiple Rainbow Sharks for aesthetics or for breeding purposes, it can definitely be done. Keep a group of five or more to prevent the dominant Rainbow Shark from targeting a single fish with his bullying behavior, and never keep just two Rainbow Sharks. If you must introduce multiple Rainbow Sharks, make sure they all have ample space to swim around the tank, increasing the volume of your tank exponentially as you add more fish.
Common Rainbow Shark Diseases
Weekly cleanings can help prevent most Rainbow Shark diseases. Use a siphon to suck up any waste on the bottom of the tank, and scrape any algae from the glass. Then, remove and replace ten to fifteen percent of the water. Avoid irregular but larger water changes, as these can alter the composition of the water and make your fish sick.
When you change the water, you do not need to remove your Rainbow Shark. This can stress your fish. Instead, replace the water by putting new water in a bucket, testing and treating it as needed.
Rainbow Sharks are prone to most of the same diseases that afflict other freshwater fish species. Most of these diseases are highly communicable and can spread quickly, so being vigilant and watchful for symptoms of disease is vital.
If you notice your fish scratching against objects in the tank or gasping for air at the surface of the water, this can indicate a potential problem. Lethargy is always a red flag, as is a loss of coloration or change in color pattern on your fish. Gills or fins that look damaged or chewed on, as well as those pressed tightly to the body, can be problematic. Finally, bloating and a disappearing fin can also be telltale signs of disease.
Breeding And Life Spans Of Rainbow Shark Danios
In the wild, Rainbow Sharks breed in October to November. To be sexually mature, a fish must be around four inches in length. Their breeding season varies slightly depending on the changing of seasons, along with day length and temperature.
Rainbow Sharks are like other fish in that they reproduce through egg laying. The female lays her eggs and the male fertilizes them by spraying them with milt. The eggs take about a week to hatch, which is relatively quick among other fish species.
Breeding Rainbow Sharks in an aquarium setting is relatively challenging, which is why most Rainbow Sharks purchased at pet stores are bred commercially on farms in Southeast Asia. The challenges in breeding Rainbow Sharks likely has to do mostly with their territorial behaviors, which make it difficult to keep multiple Rainbow Sharks confined to a tank.
With that in mind, it’s definitely worth a try. If you want to breed your Rainbow Sharks, remember the rules we already mentioned about quantities and tank setup for multiple fish, and exercise patience as you begin the process. Because it is so difficult to determine the sex of your Sharks as juveniles, you will need to wait until they age to determine whether you have males or females in your tank. Remember, females will be a bit thicker and have black lines on their fins.
Again, Rainbow Sharks aren’t ready to breed until they are a minimum of four inches in length, so attempting to breed your Sharks before then is futile. Instead, wait until they are old enough to do so, and then treat them with hormones to encourage mating. You can also feed them higher protein foods, like shrimp or tuna, or raise the temperature of your tank to encourage this natural process.
Once your fry hatch, they will need to be moved to a separate ten-gallon tank. This will eliminate the likelihood of them being harassed by other fish or by other Rainbow Sharks, and will also give them time to adjust to their new home. You can feed them liquid fry food for two weeks and then transition to baby brine shrimp. Once they have reached their juvenile stage, they can safely be introduced to the regular tank – just remember that there may be some territorial spats while they get adjusted.
Is A Rainbow Shark Right For You?
Rainbow Sharks offer so many benefits to a community tank, eating algae and offering a colorful display of activity that can liven up any setting. However, keeping Rainbow Sharks is not for the faint of heart. You need to have an acute understanding of the aggressive, territorial behaviors of these fish, and work with that knowledge to come up with a plan that will allow your Rainbow Sharks to thrive among the other inhabitants of your aquarium.
That being said, Rainbow Sharks are easy to feed and care for beyond that. They are beautiful to watch and will eat a variety of foods. If you are planning to keep Rainbow Sharks, you’ve made a great decision. These fish will live for many years and provide you with endless enjoyment and entertainment.