The small group of tropical freshwater fish known by their common name of 'sharks' have very little relation to the large predators of the oceans, but they are still an interesting group of aquarium fish
The 'shark' name comes not from any relation to marine sharks but from the fishes well-defined fins, particularly the shark-like dorsal fin, and the sleek body shape. The freshwater sharks however, can be quite a handful in their own right, and should always be chosen with care.
Freshwater sharks have plenty of character and presence and in the right environment, a freshwater shark can be a great addition to the home aquarium. In the wrong environment however, some of the freshwater sharks can become your worst nightmare.
Ruby's, red-tails, and rainbows
Perhaps the best recognised of the sharks is the Red-Tailed Black Shark (RTBS) Epalzeorhynchos bicolor
The jet-black colour of the solidly shaped body perfectly shows off the fish's well-defined 'shark-like' finnage and bright red tail, and it is this appearance that has made the fish so popular.
Although often sold as a community fish, many fish keepers have since learnt better. If it is able to, a rogue RTBS will dominate an entire tank, terrorising and harassing the other fish, especially in smaller aquaria.
A RTBS however, will only pick on the easy targets - mix a red tail with fish unlikely to feel threatened or run away, and the red tail will soon stop trying, or at least cause little more than an occasional squabble.
For this fish, robust tank mates like large barbs, peaceful cichlids, and rainbowfish are the ideal choices. Typical smaller 'community' fish, timid species, or slow moving fish will not fare well against a RTBS.
A good alternative to the RTBS is the Ruby Shark Epalzeorhynchos erythrurus, a similar looking fish with a slightly lighter and more slender body, and red colouration on all the fins. Although still a little territorial, the Ruby Shark is much more sociable and with the exception of very delicate fish, can be kept in community aquariums.
The Ruby Shark is often confused with the Rainbow Shark Epalzeorhynchos frenatus, which sports a lighter grey body and slightly different fin shape. The differences in behaviour and size between these two fish however, are not significant enough to cause concern.
We are Siamese, if you please
Although not sharing the common 'shark' name, the Flying Fox Epalzeorhynchos kalopterus
belongs to the same group of fish as the Ruby and RTBS. The Flying Fox is a sleek looking fish with a central dark bar along the entire length of the body, growing up to 15cm. It also shares the common aggressiveness found in many of the sharks - a pair of these fish will continually fight, and individual specimens will harass weaker tank mates.
In many cases the Flying Fox is purchased in mistake for the Siamese Flying Fox Crossocheilus siamensis. The Siamese Flying Fox is a much more peaceful fish and can be distinguished from the Flying Fox by transparent finnage and a stockier body. Siamese Flying Fox's are excellent algae eaters, tackling even tough fibrous thread algae and can be kept either in groups or singly in community aquariums.
The genus of Labeo contains the greatest number of fish attributed with the 'shark' affix to the common name, but few of these fish are seen as mainstay fish in the aquatics trade.
The most infamous of these sharks is the Black Shark Labeo chrysophekadion, a fish which should under normal aquarium conditions be avoided at all costs. Despite the fact that this fish will reach up to 60cm in the aquarium (90cm in the wild) it is also a territorial bully that will continually harass other fish.
The black shark is similar to the Red-tailed Black Shark in both shape and character, but with the extra power provided by its larger size it can easily tackle larger fish, leaving very little choice of tank mate. In fact, unless you own a tropical pond, or an aquarium the size of a small bus, I can recommend very little in terms of tank mates. Like the Red-tail, it is possible to come across wide variations in character, but that is a risk I would not be willing to take.
Another troublesome member of the Labeo group is the occasionally seen Harlequin Shark Labeo variegates>, a fish with a brown mottled body and fins, and orange-red coloration on the lower fins. The Harlequin Shark will reach up to 25cm in the aquarium and should only be kept with other big robust fishes. Unlike the 60cm Black Shark, this 25cm troublemaker is manageable if kept with the right tank mates.
A much more aquarium-suited fish is the Festive Apollo Shark, or Signal Barb Labiobarbus festivus
, which is a timid shoaling fish, sporting a silvery body with orange-red and black tipped dorsal and caudal fins. These fish need to be kept in groups with plenty of hiding spots and open swimming spaces. In the aquarium the Signal Barb can grow up to 20cm so a group of these fish will require a 150cm/5 foot or larger aquarium.
The well-known Silver Shark Balantiocheilus melanopterus has similar requirements although at up to at least 25cm, these fish will require a 180cm/6 foot aquarium as a minimum. Silver Sharks are an excellent addition for peaceful communities of larger fish and unlike other fish with the 'shark' name, the Silver Sharks are very peaceful and can even be mixed with significantly smaller fish.
Excluding the peaceful Apollo and Silver Sharks, all the other species mentioned here will fight with each other and can only be mixed with care. Red-tails, Harlequins, and Black Sharks should only be kept as single specimens with no other sharks. Ruby's, Rainbows, and Flying Foxes should either be kept as single specimens (one species) or as groups of four or more. Siamese Flying Foxes are a little more sociable and a pair will normally get along, but if there is trouble, simply increasing the numbers should solve any problems.
The style of decor in an aquarium and the aquariums size usually has a bearing on how well these fish get along. A large aquarium with well-defined areas of decor will allow individuals to stake out territories and keep to their own areas. With these fish it is often a case of 'out of sight, out of mind' so unless another fish is in direct sight, it will be left alone.
In a shops sales tanks you are likely to see lots of sharks inhabiting one tank, along with other community fish. Although this might contradict the aggressive territorial behaviour I have mentioned, it is possible because these are young fish. As with all fish, when young it is best to stay in groups to avoid being preyed upon, so young sharks are relatively sociable and peaceful. It is only when these fish mature after a few months that their true nature comes out.
When you choose your shark, you should look for strong colours and a stocky body, it is not uncommon to see specimens that are underfed and thin and these should be avoided. It is also quite common to see splits in the dorsal fin, but this does not seem to be an indicator of bad health so providing there are only one or two clean splits and the fins are otherwise not ragged, then these fish are fine, and the splits will heal as the fish grows.
Care & Feeding
The sharks will thrive in a wide variety of water conditions so pH and hardness levels are unimportant. Most sharks are scavengers and although they will graze on algae, they also need a varied diet containing a mixture of vegetable and meat content.
A staple diet of sinking pellets and wafers should be supplemented with live or frozen foods. As with other scavenging fish, the aquarium substrate must be either fine sand or smooth rounded gravel so that the fishes mouthparts are not damaged.
Plenty of dark hiding spots are essential, both for the fishes security and to allow territories to be established.
Identifying males and females is not easy with these fish but depending on species, females are often slightly stockier and there are occasional differences in the dorsal fin shape. Under aquarium conditions however, these fish are very unlikely to breed, partly due to their territorial nature.
Sharks are great fish for the aquarium providing they are mixed with the right tank mates, and in the correct size aquarium, and adding one of these fish to your setup will certainly liven things up a bit.