Arcadia Aquatics
  • Species: Glyptoperichthys gibbiceps

  • Species: Giant Gourami

  • Species: Megalodoras irwini

  • Species: Panaque nigrolineatus

  • Species: Distichodus lusosso

  • Species: Distichodus sexfasciatus

  • Species: Oscar

  • Species: Tinfoil Barb

The large fish community

30 March 2017


While most fish keepers start off with a small or medium sized community aquarium, populated with shoals of brightly coloured fish, many are slowly drawn across the floor of the aquarium shop to where the large fish lurk, often in solitary splendour. Although guppies are beautiful, it is hard to detect much personality in an individual, and when the question of real ‘pet fish’ comes up the stories related are usually about the giants.

However, as you gaze into the eyes of the foot-long pleco in the aquarium shop, spend a little time reflecting that many of these fish are there because they are orphans – bought when they were tiny and cute, they have reached their full size and have been returned to the shop as unwanted adults. A large fish community has much to offer the keeper in terms of fascination and often fish with distinct characters, but in return for this the aquarist must be prepared to make the outlay on suitable equipment.

For big fish there can be no skimping on filtration; a big fish has a big appetite, and a correspondingly large output from the other end… a large external filter is the best option, as weighty fish can move objects inside the tank with amazing ease. It is also necessary to protect any heaters, either with décor or by heater guards, as a large active fish can smash a heater with ease. The tank itself needs to be a minimum of six feet for the type of fish discussed here – although you could get away with a smaller tank, you would not be able to keep many fish, or be able to see them swimming about freely. Such a tank will hold a considerable weight of water, and this means that the positioning of the tank must be carefully chosen. You may get away with a small tank sitting on your antique sideboard, but a large tank will likely end up on the floor as mixed splinters of glass and wood. A purpose built stand is vital, with adequate support. Furthermore, if the floor is wooden, ensure that the weight is spread over several beams.

The décor and plants also need to be considered carefully. Any rocks ideally need to be glued into place, as a flick from a large tail could send a stone crashing against the glass with unfortunate consequences. Tough large plants are to be recommended. Java Fern is ideal for most situations – it tastes nasty, can be firmly tied to pieces of décor instead of relying on it rooting in time to stop the fish getting it out again, and if the worst happens will survive quite happily bobbing around until the aquarist can re-affix it. Amazon sword plants are also quite hardy once in place, and grow large enough to provide plant cover for large fish. Ideally the entire aquarium should be set up and the plants allowed to root properly before subjecting them to the activities of your chosen fish.

If you have decided to make the commitment to a community of big fish, then it is probably because one particular species has caught your eye. In choosing tankmates for it there are a few basic rules that will minimise future problems. Just as for a small aquarium, all the inhabitants will have to share the same home, so it is best to choose fish that have similar preferences in terms of water chemistry and habitat. However, their preferences may also cause problems – if you stock your tank entirely with a selection of fish that are likely to want to be territorial about caves, then home-ownership fights will probably result. Varying lifestyles among your fish will minimise problems. With a few exceptions, most aggressive fish are far more aggressive towards members of their own species (or those that look similar) than towards members of other species, and such aggressive fish are best kept as singles. If you want to try breeding large fishes, you are more likely to be successful with a single species tank. Finally, all the fish must be big enough! Fish have surprisingly large mouths, and in general will eat anything that they can fit inside. By making sure that your tankmates are all of roughly the same size, you can minimise the chance of ending up with an aquarium with one very fat fish.

Some of the fishes which are ideal for a large community, and too often end up as cramped outcasts from small tanks, are the suckermouth catfishes. Thousands of baby ‘plecs’ leave the aquarium shop each year destined for an unsuitable home, but these hardy, attractive and peaceful fish are ideal for a large community. Hypostomus punctatus is a peaceful and hardworking fish, that will ensure no trace of food is left on the aquarium floor during its nightly peregrinations. Growing up to a foot long, these are easily available; most shops have one or two looking for a good home. Another good choice for the large community is the red or sailfin plec, Glyptoperichthys gibbiceps. In the wild these fish are often found together, but it will nonetheless settle into an aquarium with other tankmates quite happily. It will grow up to about 20”. Slightly more shy and peaceful is Panaque nigrolineatus. It should only be kept with peaceful fishes, and grows up to just under a foot. These are very striking when young, with a sharp livery of black and grey stripes and red eyes, but the pattern will fade as the fishes grow older. All these suckermouth catfish are primarily vegetarian, and will need algae tablets or another vegetable diet. They are South American, and will prefer soft acidic water, although they will thrive in a neutral pH once acclimatised.

Another fascinating catfish for a large tank is Megaladoras irwini, a true gentle giant. This fish cannot be described as a beauty, and grows up to two feet, but will fascinate any viewer with its sculptured appearance. Each of the bony plates along the sides of the fish has a sharp scute projecting backwards, and although the fish is gentle, bloodshed will result if you try to catch it in the hands. These South American fish relish a diet of meat – daphnia, bloodworm, and earthworms will all be received eagerly. If, like me, you find that snails take up residence in a tank from no known source almost as soon as you have set it up, then this fish will happily crunch its way through the pests for you. Once again, softer water is preferred.

For an aquarium with harder water, one of the Synodontis catfish would be an attractive addition. The leopard Synodontis, Synodontis nigromaculatus, grows to about fourteen inches, and is a peaceful fish usually most active at twilight. Synodontis can sometimes be aggressive towards other territorial fish, but ensuring that yours has its own hideout in the aquarium should avoid problems. These fish enjoy all forms of flake and tablet food, but do require live food (or frozen food) sometimes to maintain them at their peak. The food should be given just after lights out, since otherwise the other fish in the tank will get a good feed and the Synodontis will find nothing when it ventures out. There are a large number of Synodontis species suitable for both large and small aquariums, so it is important to check on the size of the particular species you are buying.

The tinfoil barb (Barbus schwanfeldi) is an often unappreciated beauty. Small, nondescript juveniles will grow into fourteen inch flashes of silver with resplendent red and black fins. These are fish who relish the company of their own kind, and should be kept in a shoal of six or so. This very active fish requires lots of swimming space and soft slightly acidic water. On a varied diet they will soon show their true colours and provide a display that is always on the move. Although they may nibble aquarium plants, plenty of vegetable matter in their diet (plus a choice of tough plants) should minimise this habit.
An alternative shoaling fish to provide a good aquarium display is the silver shark, Balantiocheilus melanopterus. Silver with yellow, black-edged fins, six or more of these active fish will provide a fine spectacle. They are fast swimmers, and can be nervous. Their tendency to dart about at any disturbance necessitates a large tank if they are not to bang into the sides and damage themselves. These peaceful fish prefer a soft, slightly acidic water with a good oxygen supply, and enjoy a varied diet.

For a real conversation piece, you could keep one of the bichirs. The ornate bichir, Polypterus ornatipinnis is not only attractive, but also a fascinating fish. These fishes are proficient escape artists; like all bichirs they have a modified swim-bladder which allows them to breathe atmospheric oxygen, and if not kept in a tank with a tight-fitting secure hood are likely to take a wander around the house. Although they are predators, they are harmless to fish of the same size, and can be kept in a community with neutral or slightly alkaline water. They can be quarrelsome towards one another, so only one is recommended for the community tank. Growing up to seventeen inches, the décor for a bichir must be constructed to allow them hiding-holes in caves, rocks and plants. They have been spawned in captivity, although rarely, and a species tank for breeding would be an interesting project for an aquarist. The ornate bichir is likely to be quite expensive compared to others, due to its beautiful colouration, but all bichirs are interesting to keep. In the aquarium a meaty diet will keep them in the best of health, and they will relish such live foods as earth worms or bloodworm. The ornate bichir will grow to around 17”.

Gouramis are another group of fish that can breathe air, but are far less likely to go walkabout than the bichirs. Although many are suitable for the smaller aquarium, both the kissing gourami and the giant gourami are ideal for large tanks. The kissing gourami (Helostoma temminckii) is by nature a green fish of up to twelve inches, but there is also a pink form available in the aquarium trade. These fish acquired their common name not by their affectionate nature, but rather the opposite; the kissing displays are a way of testing their strength against one another. In the aquarium they often do not reach their full size. They prefer soft water and plant growth, which they will snack on, so plastic plants might be a better bet. If a larger fish is required, there is the giant gourami (Osphronemus goramy), which grows endearingly uglier as it increases in size. Aquarium fishes typically reach about sixteen inches (although bigger is certainly possible, especially in the wild), and are instantly identifiable with their large humped foreheads and protruding eyes. They are gentle giants, being tolerant of most water conditions, and prefer a diet of vegetables such as spinach, peas and similar foods.

If a poll was conducted of all the people who had a ‘pet fish’, Oscars (Astronotus ocellatus) would almost certainly come out near the top of favourites. These large cichlids are quite mild and self-effacing in cichlid terms, and guaranteed to add a fish with ‘personality’ to the community. Growing up to around a foot, they prefer softer water but are quite adaptable and hardy. The ‘ocellatus’ of their latin name refers to the tail markings which resemble eyes. Although the wild fish caught in South America are usually brownish, a range of colour morphs are now available for those who prefer their fish a little more brightly coloured. Oscars are attractive individuals in the community aquarium, when kept with other fish of around 15” who will not bully them. Unfortunately if they spawn they are likely to become more aggressive, and since there is no way of sexing them it is best to choose only one. This popular aquarium fish holds the affection of its owners not only by always being ready for a meal, but by awareness of the world outside the confines of its tank. Oscars who rush to the glass when their owner passes by are common. They require a meat-based diet, and will feast eagerly on live foods, prawns, whitebait, and similar offerings.

For a more colourful fish for the larger community, several of the Distichodus species grow large. Distichodus sexfasciatus is often seen for sale; although it can grow up to a metre, 10” is a more likely length. However, its early appeal can fade with its colour as it grows older. Distichodus lusosso is a sixteen inch fish with striking vertical black stripes on a gold/brown background. and can be distinguished from sexfasciatus by its longer nose. Both fish are determined plant eaters, and will devour anything palatable; Java fern or plastic plants may be suitable for the aquarium. These African fishes prefer slightly harder water.

Unfortunately in an article such as this it is impossible to cover all the wide variety of fish that could prove welcome additions to the large fish community. However, by following the normal rules of finding out as much as you can about the fish that you are buying, you too will be able to create a community of fishes that will prove striking in both their appearance and behaviour.