Top 5 Freshwater Sharks for Aquariums (and How Big They Really Get)
You may have gone to the pet store and seen some freshwater fish labeled as “sharks.” These species are not true sharks but rather are members of the Cyprinidae family of carp and minnows. They just happen to look like sharks because of their slender, torpedo-shaped bodies and pointy fins. Beginners often buy freshwater sharks because of their attractive shape and hardiness, but they can grow much bigger than expected and have large tank requirements in adulthood. So, before you take home that adorable 2-inch (5 cm) shark at the pet store, let’s learn about their requirements and see if they are the right fish for you.
1. Red Tail Shark
Also known as the red-tailed black shark or redtail sharkminnow, this species is easily identified by its entirely black body and fins with a bright red tail. While they may be sweet and small as a juvenile at the fish store, an adult red tail shark grows up to 5–6 inches (13–15 cm) and requires an aquarium that’s at least 4 feet (1.2 m) long. They come from Thailand’s rivers, streams, and floodplains during the rainy season, which means they are accustomed to living in a wide range of pH between 6–8 and temperatures from 72–79°F (22–26°C). Like all of the sharks on this list, they are omnivores that will eat almost anything — including sinking wafers, fish flakes, and even certain types of algae.
Red tailed sharks are solitary creatures and not schooling fish, so as they grow older, they become very territorial towards members of their own species and other sharks. They can handle being with other semi-aggressive, similar-sized fish — such as African cichlids, South and Central American cichlids, and larger gouramis like blue and gold gouramis. You can also pair them with slightly smaller, super-fast schooling fish, like giant danios and barbs. Avoid tank mates that are peaceful fish, slow swimmers, or nano creatures that could be eaten.
2. Rainbow Shark
This beautiful centerpiece fish also grows to 5–6 inches (13–15 cm) and looks very similar to the red tail shark. However, instead of being almost all black, they have more of a dark gray coloration with both red fins and a red tail. Plus, pet stores commonly sell different color variations, such as the albino and Glofish versions. They also come from Thailand and nearby Southeast Asian countries and can live in a broad gamut of pH levels between 6.5–8.0 and temperature from 72–80°F (22–27°C). They enjoy eating all kinds of community fish foods like pellets, wafers, blanched veggies, and frozen foods. Plus, they will opportunistically pick at algae when hungry enough.
While rainbow sharks are more social as juveniles, they eventually become semi-aggressive towards their own species and other sharks. Consider only keeping one rainbow shark per every 4 feet (1.2 m) of aquarium length. Suitable roommates include similar-sized cichlids, loaches, gouramis, and rainbowfish. But be prepared to remove certain tank mates if it doesn't work out and the rainbow shark keeps bullying them.
3. Roseline Shark
The roseline shark gets its common name from the shorter red line that lies on top of a longer black, horizontal stripe down the middle of its body. Also known as Denison barbs, they grow to 4–5 inches (10–13 cm) long and have lovely yellow and black markings on the tail. They come from fast-moving rivers and pools in India with dense vegetation near the banks and would appreciate living in a planted aquarium. Unlike the previous fish on this list, they are a schooling fish and require 3–5 or more in their party, so be prepared to get a tank that is 4 feet (1.2 m) in length or greater. As one of the smaller and more peaceful fish on this list, they would do great with rainbowfish, bigger livebearers, and other fast swimmers. You should have no problems feeding them an assorted mix of prepared, freeze-dried, gel, and frozen foods.
4. Siamese Algae Eater
Need an algae eater to cover bigger tanks? Try the 6-inch (15 cm) Siamese algae eater (SAE) that has a silvery-brown body with a bold black line down its side. It is one of the few fish that will eat black beard algae, as well as other types of algae and fish food leftovers. They tend to eat more algae as juveniles because the adults are large enough to get the lion’s share of the fish food you feed. To encourage the adults to go after algae, you may need to fast them for about a week to get them hungry enough.
SAEs come from rivers and floodplains in Southeast Asia and can easily live in pH of 6–8 and tropical temperatures of 72–79°F (22–26°C). While you can get a school of them if you need lots of algae-eating power for a large aquarium, they tend to become territorial with age towards other sharks, including their own species. They are content with living a solitary life, so you could consider keeping just one in a 50-gallon tank or larger.
5. Bala Shark
The largest shark on our list reaches 12 inches (30 cm) in size. Also known as the silver shark or tricolor shark, it has a silvery body and light-colored fins with thick, black edging. As residents of Southeast Asian rivers and lakes, they are hardy enough to live in pH between 6–8 and temperature from 72–82°F (22–28°C). They are quite easy to feed and will readily eat any floating or sinking foods, as well as invertebrates like shrimp and snails.
We do not recommend this species for most aquarists because of the enormous tank size requirement. They are constantly on the move, so you need to provide adequate swimming space for this foot-long creature. As a giant fish that prefers a school of four or more, it can be hard to get an aquarium with at least 6 feet (1.8 m) in length, so many hobbyists end up just getting one bala shark for a 125- to 150-gallon fish tank. They can be kept with other similar-sized, semi-aggressive fish like larger cichlids, catfish, loaches, and gouramis.
If you are serious about providing for a freshwater shark and ensuring it has the right tank size and tank mates, consider checking out our list of preferred retailers to buy fish online. Best of luck with your aquariums and enjoy nature daily.