Arcadia Aquatics
  • Species: Dwarf Rasbora

  • Species: Marbled Hatchetfish

  • Species: Corydoras habrosus

  • Species: Corydoras hastatus

  • Species: Corydoras pygmaeus

  • Species: Glowlight

  • Species: Melanotaenia praecox

  • Species: Otocinclus affinis

  • Species: Guppy

  • Species: Cherry Barb

  • Species: Harlequin

  • Species: Rhinogobius wui

  • Species: Golden Dwarf Barb

The small community tank

12 March 2017


In general, it is recommended that an aquarist should buy the largest tank he can afford and has room for. There are many reasons for this. The larger the tank, the slower water quality changes are, and a dead fish or piece of leftover food in a large tank will have less overall effect than one in a tiny tank. After all, a fish dying in a river has little or no effect, but a fish dying in a teacup will rapidly pollute the water. Also the larger the tank, the greater number and variety of fish can be kept.

However, this is not to suggest that a small tank is impossible to keep. If you are on a very limited budget, or only have a small amount of space, a small tank can, with care, be as beautiful and interesting as a large one. When choosing a small tank, you must be aware that the same rules apply to little tanks as to large ones. One inch of tropical fish can be kept per square inch of water surface (the length of a fish is measured from the nose to the beginning of the tail fin, and does not include the tail itself). Because of this rule, if you choose one of the taller tanks with a smaller water surface, you will be able to keep less fish than in one of the standard rectangular ones, with a greater water surface. If you choose a very small, ‘non-standard’ size, you may have difficulty obtaining a tank hood or lighting, so be sure to consider this when buying your aquarium.

Once your small tank is equipped with water, heating, filtration, and lights, you may want to choose some plants to aquascape it. If you have chosen undergravel filtration, your choice of plants will be more limited, as most plants do not like the water moving around their roots. You could choose plastic plants, or there are still some plants which will thrive even with an undergravel filter. One of these is Java moss (Vesicularia dubyana). This is an excellent plant for most aquaria, and ideal for a small one. Like the moss that grows on paving stones, it will grip to almost any surface and can be cut back without harm. Fix it in place on stones or bogwood with thread or rubber bands, and in a short time the moss will be firmly affixed. A careful choice of pieces of décor coupled with the moss can add height to your display and give a very natural effect. Anubias nana is a slow-growing plant with dark green leaves, which can either be rooted in the gravel or fixed, like Java moss, to a piece of décor, which the roots will eventually grip firmly. Like the moss, this plant will co-exist happily with an undergravel filter, and may even flower. For a tank with soft to neutral water, there is a large choice of Cryptocoryne species available. These plants often drop most of their leaves when first planted, but with a little patience and a minimum of disturbance they will flourish.

For those who have chosen to have a different form of filtration, there is even more choice. Eleocharis parva can be planted to form a low-growing lawn – the thin leaves look very like grass, but will thrive in bright lights underwater. Myriophyllum is a tall, ferny plant, which is usually chewed to pieces in an aquarium with large hungry fish. However, in a small aquarium with small gentle fish, it provides an attractive display. The stalks will grow tall, but can be pruned without ill effects, and the soft feathery leaves provide a haven for any shy or spawning inhabitants. Once the plants and décor have been added and allowed to settle for a week or so, you can then start to choose the community for your tank.

When a fish is added to a new tank, it immediately starts to pollute the water by its natural excretion processes. If you have chosen a chemical filter, then these poisons will be removed from the water, but if you have chosen a biological filter (undergravel or sponge) then the filtration cannot start immediately. This is because the filter only contains a miniscule number of bacteria, and it is the bacteria in the filter that remove the poisons from the water. As the fish starts to excrete, the bacteria will begin to multiply to take advantage of this new largesse of food, but this is a slow process. This occurs in any new tank, but in a small one, as discussed earlier, toxins in the water are less dilute and can reach fatal levels quickly. When the filter is unable to process the wastes quickly enough, the water becomes poisonous, and the fish start to die. This is known as ‘New Tank Syndrome’. You can avoid this by adding the new fish one at a time, and waiting a fortnight before adding another. There are also ‘filter start’ preparations available that contain the filter bacteria, and dosing the tank with one of these a couple of days after each new fish is added can help avoid New Tank Syndrome. Provided you are not impatient, and are careful to check water quality and perform maintenance such as removal of dead leaves and water changes, then your small fish should suffer from no problems.

There are a wide range of beautiful and fascinating fish available for the smaller tank. Some of them are described here, but there are many more. Before choosing a different fish for your community, check first to find out its adult size – many tiny fish are available in the aquarium shop that are just babies, and will rapidly outgrow your tank.

An ideal fish for a small community is the dwarf Otocinclus, Otocinclus affinis. Although not a great beauty, the charm of the Otocinclus lies mainly in its tireless efforts to keep the tank algae-free. The little catfish will often be seen attached to the tank glass, plants, or stones, munching away with its specially adapted sucker mouth. Growing only to an inch and a half, you can keep one or more of these gentle fishes. Originally hailing from the soft waters of Brazil, you can keep these fish in neutral water, and one bought from a local aquarium store will probably already be acclimatised to your local water conditions. Although they enjoy a good algae meal, there is not likely to be enough in your aquarium to keep them fit and happy, and they will appreciate extra vegetable foods such as algae tablets, cucumber, or blanched lettuce.

While the Otocinclus is a ‘slow and steady’ fish, not given to sudden activities, some of its catfish cousins will provide almost constant activity and movement, even in the daylight hours. There are many varieties of Corydoras, but three are especially suitable for a small aquarium – Corydoras hastatus, C. habrosus, and C. pygmaeus. Growing up to an inch, these endearing little fish will be unhappy and shy if kept alone, so you should allocate space for at least four or five. The school of busy little fish will nearly always be out and about, taking a lively interest as they bustle through the tank. All Corydoras are from soft South American waters, but are adaptable fish and will acclimatise to conditions from soft to neutral.

The barbs are an extensive family of fishes, and many of them grow extremely large. Nonetheless, there are several small barbs suitable for a small community. The Golden Dwarf Barb, Barbus gelius, grows only to an inch and a half, and is a peaceful and sociable fish that will fit well into a quiet community. They do prefer softer water though, so if your water tends more towards the hard side, a better choice may be the Cherry barb, Barbus titteya. These pretty red-brown fish are best kept as a pair, with plenty of plants for them to hide in. The female, although still very attractive, is more russet, while the male is bright red. Barbs are not fussy feeders, and will appreciate small live foods and flakes.

An interesting fish that is well worth considering, if you can find a shop that stocks it, is Rhinogobius wui. This little goby will give you hours of amusement and fascination, but they do need small live foods to keep them healthy. Growing up to about one and a half inches, the male is a chocolate-brown with red throat markings, while the females are a paler brown. If a few flat stones are placed on the gravel, the male will dig a hole underneath and seal himself in. When this happens, he usually has a crop of eggs, each glued to the underside of the stone by a little stalk. They are active aquarium inhabitants, and can be seen perched on plants or rocks, or bounding across the substrate in a most unfishlike way.

Many rasboras are on the small side, and most are very beautiful and striking fish. The Harlequin, Rasbora heteromorpha, is easily available from nearly every aquarium shop. Growing up to an inch and three quarters, these sociable fish prefer to be kept in a group. Ones bought locally will usually be acclimated to your water conditions, although naturally they prefer softer water. The black triangles over the back half are surmounted with an iridescent red line, which flashes as the fish move around the tank. Slightly less easy to obtain, but just as beautiful, is the one inch Dwarf Rasbora, Boraras maculata. These are a beautiful intense red with black markings, and provide a fine spectacle in a small group. The group may be kept with other small Rasboras, or other quiet fish. Like most fish, Rasboras relish the occasional treat of small live foods, but will also enjoy flake foods.

Tetras, especially neons, are the fish that often comes first to mind for people whose sole experience of tanks is in the dentist’s waiting room. Such tanks nearly always include some neons, and indeed the spectacle of their iridescent glowing blue lines succeeds in taking most people’s minds off their problems for a while. Neons (Paracheirodon innesi) grow to about an inch and a half, and are slightly smaller and hardier than their cousins the Cardinal tetras. Although they prefer soft water, and will not breed in harder water, they nonetheless acclimatise well and will be a valued addition to the small community. Most tetras are schooling fish, and you will need several. Another tetra ideal for the small community is the Glowlight (Hemmigrammus erythrozonus). While the neons flash their blue stripes, the glowlight is adorned with a luminous red stripe. In a dark aquarium both these tetras will be seen at their best, and it will seem as though lights are gleaming out of the shadows as the fish move.

These South American residents fit in well with another South American fish, the Marbled Hatchetfish (Carnegiella strigata). Although some hatchets grow a little larger, the Marbled Hatchetfish is an ideal size at an inch and a half. These fish guarantee some movement in the upper layers of the water, as they spend their entire lives at the surface. A tightly fitting tank lid is essential, as the fish are quite capable of ‘taking flight’ if startled, and can travel considerable distances through the air and out of the tank! It is essential that they are fed very small floating foods, as the hatchet fish have tiny mouths and will not dive for food – as soon as it has left the surface it is out of their reach. Hatchetfish are both attractive and unusual, and the little bit of extra care to ensure they are eating properly is well worth the effort.

Another fish of exceptional beauty is the Neon Rainbowfish, Melanotaenia praecox. Although many rainbowfish grow quite large, and are unsuited for a small tank, these little jewels stop growing at around two inches. The male is exceptionally attractive, being a bright blue with scarlet fins. The females are coloured similarly, but not as brightly. These active and peaceful fish prefer softer water, and can be kept as a pair or small group. Although once these were rarely seen, and were sold for outrageous prices, you can now obtain them much more easily and without mortgaging your home!

Livebearers are always interesting in the aquarium, and many of the common species will breed easily and prolifically. The popular guppy, Poecilia reticulata, is especially easy to breed, and the females will nearly always be pregnant. If you choose to keep this fish, remember to check your aquarium population carefully and regularly – if too many fry grow to adulthood then your small aquarium may become overpopulated and polluted. The females are much larger than the males, and can grow to two and a half inches, while the males are only an inch long. It is only the males who exhibit the beautiful markings, so in a small tank it may be best to keep only males (thus ensuring the overpopulation problem never arises). If you do decide to keep both sexes, then the females must outnumber the males, or they will be harassed unmercifully by the males who are always on the lookout for a chance to mate. A more unusual fish, the Dwarf Swordtail (Xiphophorus pygmaeus) is not so easy to spawn, and requires a quiet environment. Although their name is a misnomer, as the male does not have the long tail extension of their larger Swordtail cousins, they are still attractive fish and can be found in a gold variant. All livebearers appreciate live foods, although most foods available will be happily eaten.

Whatever fish you choose for your mini-aquarium, by taking proper care of them and considering their needs your tank can be as beautiful as a much larger one. Indeed, if you later have the space or the money to expand, you may find that the new larger tank is still stocked with the tiny and beautiful fish that can make a small aquarium a microcosm of beauty and interest.