Pet-Shop 'Sharks': What They Really Are and How Big They Get

The small "sharks" in pet-shop tanks look like tiny sharks, but most are not sharks at all. They are ordinary freshwater fish named for their shape [1][2][3][4]. Some stay small. Others grow far bigger than a home tank, and one can reach about 130 cm [2]. Here is how to tell them apart before you buy.

How big do pet-shop sharks get?

In the shop they are usually small young fish, and nothing about them hints at their adult size. This table shows what each one becomes.

Are aquarium sharks real sharks?

Most are not. The bala, iridescent, red-tailed black and rainbow "sharks" are bony fish from the carp and catfish families [1][2][3][4]. They earned the name from their torpedo-shaped body, tall back fin and fast swimming [1][2][3][4].

In Saudi shops and listings you may see them as سمك القرش النهري ("river shark"), قرش الزينة ("ornamental shark") or البالا شارك ("bala shark"). These names usually mean one of the four freshwater fish above.

Real sharks belong to a different group of fish with skeletons made of cartilage. Only a few small kinds, mainly bamboo and epaulette sharks, are sold, and only for large saltwater tanks [5].

Tip: ask for the fish's scientific name. "Shark" covers several very different fish, and the scientific name tells you the adult size.

Which aquarium sharks outgrow a home tank?

• Iridescent shark: the biggest by far. It can reach about 130 cm and 44 kg [2]. It is the same species farmed for food and sold as "swai" or "basa" fillets [6]. Few homes can hold a fish this size.
• Bala shark: reaches about 35 cm and should live in a group of 5 or more, which needs a tank over 150 cm long [1].
• Real bamboo and epaulette sharks: about 1 m or more as adults, and they can quickly outgrow home systems [5].
• Red-tailed black and rainbow sharks: the smallest, at about 13–15 cm [3][4]. They still need space, because adults defend their territory [3][4].

What tank does an aquarium shark need?

Plan for the adult fish, not the one in the shop.

• Tank length (adult): over 150 cm for a bala group [1] and for the iridescent shark [2]; at least 120 cm for a rainbow shark [4]. An adult iridescent shark is almost as long as that tank.
• Water: all four freshwater kinds come from tropical rivers in Southeast Asia and live in roughly 22–28°C water [1][2][3][4].
• Water quality: stress, poor water quality and overcrowding are leading factors behind most aquarium fish disease [7]. A fish in a tank too small for its adult size faces exactly these risks.

Saudi heat (our reasoning, not a sourced recommendation): our sources don't cover Saudi summers. As a reasonable precaution, keep the tank out of direct sun and away from hot outside walls, and aim for steady water within the range above.

Can aquarium sharks live together or with other fish?

It depends on the kind.

• Red-tailed black and rainbow sharks: adults are solitary and territorial. They won't accept another of their own kind, or each other, in the same tank [3][4]. Keep one per tank.
• Bala and iridescent sharks: the opposite. They are schooling fish and should be kept in groups of 5 or more, not alone [1][2]. That is a big reason they need such large tanks.

What do aquarium sharks eat?

In the wild, the red-tailed black shark eats plant matter and small animals from the riverbed [3]. The rainbow shark grazes on algae and tiny plants and animals in the water [4]. The bala shark eats tiny plants, small crustaceans, insects and larvae [1]. Ask the seller or a fish vet for a suitable diet for your species.

Can I keep a real shark at home?

Only with expert skill and a very large marine setup. A University of Florida guide for aquarium buyers says plainly that "the novice aquarist should not consider maintaining sharks in an aquarium because much experience is necessary" [5].

• What they are like: bamboo sharks are active at night and live on the bottom. They are generally calm with fish but may attack shrimp and other invertebrates [5].
• Tank size: the guide's rule of thumb is the shark's adult length times 3, for both the tank's length and width [5]. For a bamboo shark of about 104 cm, that is roughly 3 m by 3 m [5].
• Feeding: bamboo sharks are among the easier sharks to settle and feed, but other kinds can be hard [5].

What if my shark outgrows its tank?

Never release it into the sea, a lake, a wadi, a drainage channel or any other outdoor water. The US Geological Survey has found iridescent sharks living wild in waterways in Florida and Illinois, most likely after people released them from aquariums [6]. Their effect on local wildlife is not yet fully studied, so the risk is real, not ruled out [6].

Instead, ask the shop where you bought it, a local fishkeeping group, or an aquarium society whether they can help you find it a responsible new home. The best plan is to choose a fish whose adult size fits your tank from day one.

Are aquarium sharks endangered?

Some are threatened in the wild, which is a different question from the fish in shops.

• Red-tailed black shark: listed as Critically Endangered in the wild. It was thought extinct there from 1996 until it was found again in 2011 [3]. Water pollution is named as the main current threat, and fish for the ornamental trade are reported to be captive-bred [3].
• Bala shark: listed as Vulnerable. It has become rare or vanished from many rivers in its native range [1]. Collection for aquariums is named as a possible cause, alongside other factors, but this is not proven [1].
• Iridescent shark: listed as Endangered in the wild [2], even though the species is farmed at large scale [6].
• Rainbow shark: listed as Least Concern [4].

Fish sold in shops are mostly bred on farms, not taken from the wild [1][2][3]. Buying a captive-bred fish is not the same as harming wild populations. We could not confirm that every fish in the trade is captive-bred, though, so a reputable seller who can tell you where the fish came from is the better choice.

We also could not confirm from official CITES records whether any of these species are listed under the international wildlife-trade treaty. Before importing, check the official CITES database or ask MEWA or the National Center for Wildlife (NCW).

How do I know if my aquarium shark is healthy?

The RSPCA lists these signs of a healthy fish, at the shop and at home [8]:

• A good appetite and steady, rhythmic gill movement.
• Active, alert behaviour and even swimming.
• Clear eyes, whole fins and smooth scales.

If something looks wrong, check the water quality first, then contact a specialist fish vet for diagnosis or treatment rather than guessing at home [8].

What should I ask before buying an aquarium shark?

• What is its scientific name? It tells you which "shark" it really is [1][2][3][4][5].
• How big will it be as an adult? Plan for that size, not the shop size [1][2][3][4][5].
• Does it live alone or in a group? Some must be alone, others need 5 or more [1][2][3][4].
• What tank and filtration will it need as an adult? [1][2][4][5]
• For a real shark: do you have real experience with marine sharks? If not, the guidance is not to try [5].
• Is it healthy? Look for the signs above [8].
• Where was it bred? Ask for a captive-bred fish from a known source. We couldn't confirm that every fish in this trade is captive-bred, so a seller who knows the fish's origin is the safer choice [1][2][3][9].

Costs to plan for: a tank sized for the adult fish (or group), strong filtration, a heater with a thermostat, a water test kit, suitable food, and fish vet visits when needed. A real shark adds a full marine system on a very large scale [5].

Can I buy or import aquarium sharks in Saudi Arabia?

Confirm first; we can't give steps for this. Animal imports and the wildlife trade in Saudi Arabia usually fall under the Ministry of Environment, Water and Agriculture (MEWA). MEWA has published documents on importing fish for aquaculture and on trade in wildlife species, but we could not read their text, so we don't quote any rule from them [9][10]. One unofficial English translation of MEWA's pet-import rules names only dogs and cats, not fish [11].

Please check the current requirements directly with MEWA or the National Center for Wildlife (NCW) before buying a rare species, importing live fish or travelling with one. This is guidance only, and rules can change.

Aquarium shark fun facts

• The "shark" in these fish's names is only about looks: a torpedo body, a tall back fin and fast swimming [1][2][3][4].
• The iridescent shark sold as a pet is the same species sold in supermarkets as "swai" or "basa" fish fillets [6].
• The red-tailed black shark was thought to be gone from the wild for about 15 years before it was found again [3].
• Bala sharks come from rivers in Southeast Asia, including the Mekong, and from Sumatra and Borneo [1].

Aquarium shark FAQ

Are the sharks in pet shops real sharks?

Usually not. Bala, iridescent, red-tailed black and rainbow "sharks" are freshwater bony fish named for their shape [1][2][3][4]. Real small sharks are rare and kept only in large marine tanks [5].

How big does a bala shark get?

Up to about 35 cm, measured without the tail. It lives in groups of 5 or more, which needs a tank over 150 cm long [1].

How big does an iridescent shark get?

Up to about 130 cm and 44 kg [2]. It outgrows almost any home aquarium.

What is the difference between a red-tailed black shark and a rainbow shark?

They are close relatives, both small (about 13–15 cm) and territorial [3][4]. The red-tailed black shark is native only to a few river basins in Thailand, while the rainbow shark comes from several rivers, including the Mekong [3][4]. Don't keep them together [3][4].

Can two aquarium sharks live in one tank?

Not two red-tailed black or rainbow sharks [3][4]. Bala and iridescent sharks are the opposite and should live in groups [1][2].

Can I release my shark if it gets too big?

No. Released iridescent sharks have turned up in US waterways, and their effect on local wildlife is still unknown [6]. Find it a responsible new home instead.

Is it illegal to buy an aquarium shark in Saudi Arabia?

We found no confirmed rules either way for these fish. Buy from a properly licensed shop, and check with MEWA or the NCW before buying a rare species or importing one [9][10][11].