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Hard Water Community Tank Options

by Neale Monks

One of the first things new aquarists learn about is the difference between soft water and hard water. Put simply, hard water contains more dissolved minerals than soft water. This is important because most fish are adapted to either soft water conditions or hard water conditions, and relatively few species do well in both. So newcomers to the hobby are usually instructed to test their tap water to determine whether it's hard or soft.

Testing water chemistry isn't difficult; there are plenty of inexpensive and easy to use test kits available. The tricky part comes next, when the aquarist wants to choose fish species adapted to their particular water chemistry. Few retailers make a point of stating whether a particular fish needs soft or hard water, which is why researching a fish species before purchase is so important.

As a rule, fish from South America, Southeast Asia and West Africa need or at least prefer soft, acidic water conditions, typically 2-10 degrees dH, pH 6-7. In other words, the vast majority of tetras, barbs, rasboras, Danios, gouramis, loaches, Corydoras, and dwarf cichlids will be healthier and easier to keep when maintained in soft, slightly acidic water conditions. Given that these fish make up the majority of community fish, aquarists with soft water on tap will find stocking a community aquarium particularly easy.

But what do you do if you have hard water? Taking the United States for example, aquarists in the states of Arizona, Florida, Indiana, Iowa, Nebraska, New Mexico, South Dakota, Utah, Wisconsin and Wyoming will all likely have tap water that is moderately hard to very hard. People living in this parts of the US will likely already be familiar with some of the problems hard water can cause, and may even use a domestic water softener to reduce the hardness of water used for washing and laundry.

If your water is only moderately hard, say, 10-15 degrees dH in hardness and with a pH of between 7 and 7.5, you might get away with keeping the hardier soft water fish species without any serious problems. But water that's very hard, typically water drawn from a chalk or limestone aquifer, will be much too alkaline for soft water fish. Instead, it's much better to choose fish pre-adapted to hard, alkaline water conditions. Central American livebearers are the most famous hard water community fish, but there are lots of others, and in this article, we'll look at some of the best of them, species that you can rely on to do well in hard water between 15-25 degrees dH and with a pH between 7 and 8.

Tetras

Although the characins from the soft, acidic rivers of the Amazon and Orinoco basins are the best known, this important group of fish is actually much more widespread than that. Among the South American species there are several that inhabit the coastal regions of Guyana and Suriname where the water can be quite hard, sometimes even slightly saline. There are characins found further north, too, in the hard, alkaline streams that criss-cross Central America, and on the other side of the Atlantic are the African characins, many of which are very adaptable and able to tolerate surprisingly hard water conditions.

African Long-Finned Tetra Brycinus longipinnis
These laterally-compressed fish are basically silvery-gold in colour, but shimmer very beautifully under subdued lighting and in well-planted tanks. Males have unusually long dorsal fins. Both sexes have an elongated black patch that runs across the caudal peduncle into the central part of the tail fin. Boisterous, gregarious fish well-suited to community tanks alongside other fish of similar size. Not a pronounced fin-nipper, but shouldn't be trusted with long-finned or slow-moving tankmates. Keep in groups of at least six specimens. Jumpy! Needs lots of space, and should not be kept in tanks less than 120 cm/48 inches in length. Water chemistry: 2-20 degrees dH, pH 6.0-8.0. Temperature: 24-26 C/75-79 F. Diet: Flake, small pellets, small live foods.

Black Widow Tetra Gymnocorymbus ternetzi
Hardy, adaptable South American tetra now widely farmed in both their standard grey-and-silver and albino forms. Dyed varieties, known as Jelly Bean Tetras, are also sold, but the method of production is cruel and they should not be purchased. Gets to about 8 cm/3 inches in length. Can be a good community fish when kept in groups of at least six specimens, in smaller groups this species is prone to nipping the fins of slow-moving tankmates. Otherwise an easy to maintain species that has been popular for decades. Water chemistry: 2-20 degrees dH, pH 6.0-8.0. Temperature: 20-28 C/68-82 F. Diet: Flake, frozen foods, small live foods.

Blind Cave Tetra Astyanax mexicanus
This pink, eyeless tetra comes from underground streams in Mexico where it feeds on bat droppings. It is not difficult to keep despite is bizarre appearance and can make an excellent community tank resident, though it dislikes warm water. It is restless though, and may nip at slow-moving tankmates. May be kept singly or in small groups, and makes a particularly good choice for life alongside fish that prefer dark aquaria, such as catfish. Maximum length is about 8 cm/3 inches, but often smaller. Water chemistry: 10-25 degrees dH, pH 7.0-8.0. Temperature: 20-25 C/68-77 F. Diet: Anything, with small meaty foods particularly enjoyed.

Bloodfin Tetra Aphyocharax anisitsi
As their name suggests, these silvery fish have scarlet fins. Although not as colourful as some tetras, they are extremely hardy, and this has ensured their popularity for over a century. In groups of six or more they are basically peaceful, though occasionally nip at the fins of slow-moving tankmates. Take care not to keep them to warm! Given good care, these tetras can live for 5-10 years. Very jumpy, so not suitable for open-topped tanks. Maximum length is about 5 cm/2 inches. Water chemistry: 2-25 degrees dH, pH 6.0-8.0. Temperature: 20-26 C/68-79 F. Diet: Flake, frozen foods, small live foods.

Nurse Tetra Brycinus nurse
A tough, greedy fish best suited to jumbo community tanks. Gets rather large, 15-20 cm/6-8 inches, so will bully weaker fish and eat very small ones. But otherwise gets along well with cichlids, catfish, barbs and loaches of similar size. Keep in groups of six or more specimens. Easy to keep, but jumpy, and needs lots of space; its tank should be at least 120 cm/48 inches long. May nibble on soft leaves, but works well alongside robust plants such as Amazon swords, Vallisneria, etc. Water chemistry: 5-25 degrees dH, pH 6.0-8.0. Temperature: 22-28 C/72-82 F. Diet: Flake, small pellets, frozen foods, etc.

(False) Penguin Tetra Thayeria boehlkei
Curiously, the true Penguin Tetra, Thayeria obliqua, is hardly ever traded. Almost all the Penguin tetras sold today are a second species, Thayeria boehlkei. The two species are easy to tell apart: on the 'true' Penguin Tetra the black band is basically limited to the lower lobe of the tail fin, whereas on the 'false' Penguin Tetra, the black band runs forward along the flank almost to the eye. Another difference is in their hardiness, the 'false' Penguin Tetra being an adaptable and easy to keep species, very different to the delicate 'true' Penguin that must be kept in soft, acidic water to do well. Maximum length of both species is about 6 cm/2.4 inches, but they sometimes get a little larger. 'False' Penguin Tetras are basically peaceful when kept in groups of six or more specimens,Â Water chemistry: 2-25 degrees dH, pH 6.0-8.0. Temperature: 22-28 C/72-82 F. Diet: Flake, frozen foods, small live foods.

Red-Eye Tetra Moenkhausia sanctaefilomenae
These tetras are quite small, 4.5 cm/1.8 inches in length, but their silvery bodies and bright red eyes make them very attractive. They are hardy and easy to keep, but a bit nippy, so tankmates should be chosen with care. Otherwise unproblematic if kept in groups of at least six specimens. Looks especially good in a planted tank with lots of shade. Water chemistry: 2-20 degrees dH, pH 6.0-8.0. Temperature: 22-28 C/72-82 F. Diet: Flake, frozen foods, small live foods.

X-Ray Tetra Pristella maxillaris
Surely one of the best tetras in the trade, this is a superb species for community tanks. Wild-type fish have transparent bodies, fins with black, white, and yellow markings, and reddish tips to their tail fins; a yellowy albino form is also available. X-Ray Tetras are peaceful, adaptable, eat anything, and can thrive in surprisingly hard water. Gets to about 5 cm/2 inches long. Keep in groups of at least six specimens. Water chemistry: 2-30 degrees dH, pH 6.0-8.0. Temperature: 24-26 C/75-79 F. Diet: Flake, frozen foods, small live foods.

Barbs and danios

Barbs are omnivorous fish adapted to shady rainforest streams with lots of plants and have laterally-compressed bodies and a single pair of short barbels. Danios are adapted to streams, ponds and canals and spend much more time in open water. They like to feed from the surface, but do have a pair of barbels and will sometimes root about on the bottom. Both barbs and danios are schooling fish, and some will cause trouble if they are not kept in sufficient numbers.

Asian Rummynose Sawbwa resplendens
This charming fish has only recently become widely available but makes a good addition to communities of small, peaceful fish. Unlike a lot of Southeast Asian species it comes from an upland region with quite hard water. It isn't difficult to keep, but dislikes warm water and is likely to be bullied by larger fish. Males and females are very different: males are blue with a red snout, whereas females are colourless and semi-transparent. Maximum length is barely 2.5 cm/1 inch. Very gregarious, but the males squabble, so keep in large groups of ten or more specimens with females outnumbering males. Water chemistry: 10-20 degrees dH, pH 7.0-8.0. Temperature: 20-25 C/68-77 F. Diet: Flake, frozen foods, small live foods.

Celestial Pearl Danio Danio margaritatus
This species was discovered as recently as 2006, but quickly become a firm favourite among aquarists all over the world. In its natural habitat in Burma it lives in moderately hard, slightly basic water, but has proven to be quite adaptable. The main thing with this species is to choose tankmates with care; it is so small that even slightly larger tankmates can bully it or steal its food. Needs to be kept in schools of six or more specimens. Maximum length is about 2 cm/0.8 inch. Water chemistry: 5-20 degrees dH, pH 6.5-8.0. Temperature: 20-25 C/68-77 F. Diet: Finely powdered flake, small live foods.

Cherry Barb Puntius titteya
Unusually for barbs, these don't really school together, and instead the females form loose gangs while males hold small territories around the tank. The males are cherry red whereas the females are pale pink. Ideally, keep a group of three or more males alongside three or more females. That way, the males will show their best colours. Maximum length is about 5 cm/2 inches. Water chemistry: 2-20 degrees dH, pH 6.0-8.0. Temperature: 22-28 C/72-82 F. Diet: Flake, frozen foods, small live foods.

Pearl Danio Danio albolineatus
Less often kept than the Zebra Danio, but well worth keeping. Colours are variable and depend on ambient conditions, but essentially pearly-pink with hints of orange and violet, particularly along the back half of the flanks. Must be kept in groups of at least six specimens. Maximum length is about 5 cm/2 inches. Hyperactive; needs a tank at least 60 cm/24 inches long. Water chemistry: 2-20 degrees dH, pH 6.0-8.0. Temperature: 20-25 C/68-77 F. Diet: Flake, frozen foods, small live foods.

Tiger Barb Puntius tetrazona
This popular species prefers soft water but the farmed specimens are adaptable and can do well in moderately hard water. They have a bad reputation for fin-nipping, but in fairness this is mostly a problem when they aren't kept in sufficient numbers. Keep six or more and they'll generally keep themselves to themselves. Maximum length is about 6 cm/2.4 inches, but needs a spacious tank at least 60 cm/24 inches long. Water chemistry: 2-20 degrees dH, pH 6.0-8.0. Temperature: 20-25 C/68-77 F. Diet: Flake, frozen foods, small live foods.

Zebra Danio Danio rerio
Famously undemanding, this is one of the most popular aquarium fish in the world. The wild-type is silvery with blue and yellow horizontal bands; an artificial form with spots rather than stripes is known as the Leopard Danio ('Danio frankei') and makes an interesting alternative. Albino and fluorescent 'Glofish' varieties are also available. Lively, but can be a bully towards smaller fish, especially when bored, so keep in groups of at least six specimens. Must have plenty of swimming space, i.e., a tank at least 60 cm/24 inches in length. Water chemistry: 2-20 degrees dH, pH 6.0-8.0. Temperature: 20-25 C/68-77 F. Diet: Flake, frozen foods, small live foods.

Rainbowfish

Rainbowfish are members of the order Atheriniformes, and while they may belong to several different families, they are all small, schooling fish with two dorsal fins. Sexual dimorphism is common, with males usually being more colourful than the females. All rainbowfish need to be kept in groups of six or more specimens. Sometimes the males are aggressive towards each other, so it's important to keep at least as many males as females, even if the females aren't as pretty (having the females there will actually encourage the males to show their best colours). Most of the species aquarists keep come from New Guinea and Australia, but some come from Madagascar and Southeast Asia.

Blue Rainbowfish Melanotaenia lacustris
This species comes from the Lake Kutubu region of New Guinea and is sometimes called the Lake Kutubu Rainbowfish. It is a beautiful species, both genders being blue in colour, though the males being considerably more intensely coloured than the females. Note though that juvenile fish aren't nearly as colourful as adults! Maximum length is about 10 cm/4 inches. Water chemistry: 10-20 degrees dH, pH 7.0-8.0. Temperature: 24-28 C/75-82 F. Diet: Flake, frozen foods, small live foods.

Boeseman's Rainbowfish Melanotaenia boesemani
One of the most popular rainbowfish appreciated for its brilliant colours and peaceful behaviour. Adults get to about 10 cm/4 inches in length and are still blue on the front half, and orange or yellow on the back half. Water chemistry: 10-20 degrees dH, pH 7.0-8.0. Temperature: 24-28 C/75-82 F. Diet: Flake, frozen foods, small live foods.

Celebes Rainbowfish Telmatherina ladigesi
This transparent species has an electric blue strip along the back half of its flank together with yellow fins marked with black. Can get to about 8 cm/3 inches in length, but often smaller. Like other rainbowfish it is very peaceful but lively, and will need a reasonable amount of space for swimming despite its comparatively small size; a tank at least 75 cm/30 inches in length is recommended. Some older aquarium books indicate that this is a brackish water species, but that is incorrect; while this species tolerates slightly brackish water well, it does perfectly well in hard, alkaline water. Water chemistry: 10-20 degrees dH, pH 7.0-8.0. Temperature: 22-28 C/72-82 F. Diet: Prefers small live foods and wet-frozen foods, but will take good quality flake too.

Dwarf Rainbowfish Melanotaenia praecox
Native to New Guinea, this species is now widely bred on fish farms and a regular offering in aquarium shops. It is not quite as hardy as some of the larger species, but not difficult to keep, and its small size ensures its popularity. Adults can get to about 8 cm/3 inches in length but are usually smaller. Males and females are similar, metallic blue with reddish-purple dorsal, anal and tail fins, but males do tend to be deeper bodied and often more intensely coloured. Water chemistry: 10-20 degrees dH, pH 7.0-8.0. Temperature: 24-28 C/75-82 F. Diet: Flake, frozen foods, small live foods.

Eastern Rainbowfish Melanotaenia splendida
This is one of the many Australian species that are traded from time to time. They are fairly large, getting to about 15 cm/6 inches, and have silvery bodies covered with red and blue speckles; their fins are marked with red, green and blue. These fish are hardy and easy to keep, but given their size, will need plenty of swimming space, realistically, a tank at least 120 cm/48 inches long. Water chemistry: 10-20 degrees dH, pH 7.0-8.0. Temperature: 22-28 C/72-82 F. Diet: Flake, frozen foods, small live foods.

Lake Tebera Rainbowfish Melanotaenia herbertaxelrodi
This medium-sized species only gets to about 9 cm/3.5 inches in length. Males are yellowy-green with orange dorsal, anal and tail fins and a blackish band running from the head to the caudal peduncle. Females are similar but have weaker colours. Basically easy to keep, but like all rainbowfish this beautiful species only shows its best colours when mature and if properly maintained. Water chemistry: 10-20 degrees dH, pH 7.0-8.0. Temperature: 24-28 C/75-82 F. Diet: Flake, frozen foods, small live foods.

Madagascan Rainbowfish Bedotia geayi
Madagascan rainbowfish are unusual among rainbowfish in naturally inhabiting soft, slightly acidic rainforest streams in the wild. Nonetheless they can do quite well in moderately hard water, providing water quality is good and that there is plenty of oxygen in the water. Males and females look similar, but males do tend to be slightly more colourful. As always, keep in a large group of males and females for best results. Water chemistry: 5-15 degrees dH, pH 6.5-7.5. Temperature: 22-24 C/72-75 F. Diet: Flake, frozen foods, small live foods.

Killifish and ricefish

Killifish can be divided into two sorts, the annual species and the non-annual species. On the whole the annual ones are demanding fish that require soft, acidic water conditions and cannot be kept in community tanks. However, the non-annual species are often adaptable and quite easy to keep, and at least some species can work well in community tank situations. Killifish tend to be jumpy and should not be kept in open-topped tanks.

Asian Killifish Aplocheilus lineatus
Although the wild-type fish is pretty and still traded regularly, an artificial form known as the Golden Wonder Killifish is much more commonly seen. In both cases this species exhibits strong sexual dimorphism, the males being more colourful than the females. This species is strongly predatory and will eat any small tankmates that come into range, so needs to be kept with tankmates of similar size. Maximum length is 10 cm/4 inches though commonly smaller. Asian Killifish are territorial and like to lurk in a shady corner of the tank; best kept singly or as a mated pair. They dislike strong currents. May be kept in slightly brackish as well as hard water. Very jumpy! Water chemistry: 5-20 degrees dH, pH 6.5-8.0. Temperature: 24-26 C/75-79 F. Diet: Will eat flake and small pellets, but appreciates small live and wet-frozen foods.

Florida Flagfish Jordanella floridae
This brightly-coloured species is easy to keep provided the aquarium is not too warm. Possible tankmates include danios and Corydoras that also appreciate cool conditions. Can get to about 5 cm/2 inches in length, but females are often smaller. Sexually dimorphic; males bigger and more colourful, while females are smaller and have a distinctive dark spot on the trailing edge of the dorsal fin. Males can be aggressive towards each other, so in small tanks keep just one male. May be kept in slightly brackish water, but does well in hard water too. Water chemistry: 10-20 degrees dH, pH 7.0-8.0. Temperature: 18-25 C/64-77 F. Diet: Algae-based flake food as well as small wet-frozen and live foods.

Playfair's Panchax Pachypanchax playfairii
Less frequently traded than in the past, but attractive and worth hunting down. Sexually dimorphic; males very colourful, yellowy with numerous red and blue spots; females similar but less intensely coloured. In general terms care is like that of the Asian Killifish discussed above, but this species appreciates cooler water and may be a bit more aggressive. Water chemistry: 5-20 degrees dH, pH 6.5-8.0. Temperature: 22-25 C/72-77 F. Diet: Will eat flake and small pellets, but appreciates small live and wet-frozen foods.

Javanese Ricefish Oryzias melastigma
Ricefish are peaceful schooling fish that work well in small community tanks alongside other tiny and very peaceful community tank species. This species is greyish-white with bright blue eyes. Males differ from females in the shape of their anal fin, which is longer and has a ragged appearance thanks to fin ray extensions. Males get to about 4 cm/1.6 inches in length, females very slightly less. This species will spawn readily in community tanks, and after spawning the females carry around bunches of fertilised eggs on their anal fins, rubbing the eggs off on plant leaves, particularly fluffy things like Java moss. The tiny fry may afterwards be spotted among floating plants, and these are fairly easy to rear on powdered fry food. This ricefish can be kept in both freshwater and slightly brackish water. It is hardy and adaptable, but does not like very warm water. Water chemistry: 10-20 degrees dH, pH 7.0-8.0. Temperature: 20-25 C/68-77 F. Diet: Flake, frozen foods, small live foods.

Corydoras

Although most Corydoras will adapt to moderately hard water (around 15 degrees dH, pH 7.5) the two best species for really hard water are the Bronze and the Peppered Catfish, both of which are mass produced on farms and widely available. Like other Corydoras, they need to be kept in groups of five or more specimens. Different species will sometimes school together, but it's best to keep at least five of each species, even if you want to keep two or more different species. While often sold as 'scavengers' it's important to remember that these fish need their own food, typically sinking pellets offered 4-5 days a week. All catfish prefer soft, sandy substrates (silica sand or pool filter sand is ideal) and if kept in tanks with gravel substrates tend to have shorter barbels than otherwise. Besides being better for them, it's also fun to watch these catfish digging into sand, spewing it out through their gills as they sift out morsels of food.

Bronze Catfish Corydoras aeneus
Bronze Catfish are among the most popular catfish in the trade and make excellent community tank residents. As their name suggests, they are greenish-gold in colour. Besides the wild-type, Neon Gold and Neon Green forms are also available. These are supposedly geographical variants and are similar in terms of care, but may be a little less hardy than the farmed Bronze Catfish seen in most pet shops. Some of the Albino Catfish on sale may be Corydoras aeneus, but are more often Corydoras paleatus, discussed below. Peaceful, but may be harassed by nippy or aggressive tankmates. Maximum length is 7 cm/ 2.8 inches, though farmed specimens are usually much smaller. Water chemistry: 2-20 degrees dH, pH 6.0-8.0. Temperature: 20-25 C/68-77 F. Diet: Sinking foods including catfish pellets and algae wafers.

Peppered Catfish Corydoras paleatus
The wild-type fish is silvery with black spots, but a pinkish-white Albino Catfish is also widely traded. In the wild this species can get to about 7 cm/ 2.8 inches in length, but aquarium specimens are usually much smaller, typically 5 cm/2 inches long. Sexual dimorphism is typical for the genus: males being smaller than the females but having much taller dorsal fins. Water chemistry: 2-20 degrees dH, pH 6.0-8.0. Temperature: 18-25 C/64-77 F. Diet: Sinking foods including catfish pellets and algae wafers.

Suckermouth catfish

The family Loricariidae contains around 800 species noted for their armoured bodies and sucker-like mouths. Most live in flowing water habitats where they feed on algae and tiny invertebrates. Although often sold as algae-eaters, their value in this regard is often misunderstood. Even those species that do eat algae will need other foods as well, for example cooked peas, cooked spinach, blanched lettuce, sliced cucumber and sliced courgette (zucchini).

Bristlenose Catfish Ancistrus sp.
The best suckermouth catfish for the general community tank, and a much better choice than the Common Plec. The wild-type fish is dark grey with white spots when young, becoming mottled brown with age; an Albino form is also available. Gets to about 12 cm/5 inches in length. Males develop long rubbery tentacles on their heads; females sometimes have these tentacles, but they won't be anything like as well developed. Very peaceful, but territorial. A good algae-eater that consumed diatoms and green algae; does need its own food though! Â Water chemistry: 2-20 degrees dH, pH 6.0-8.0. Temperature: 22-28 C/72-82 F. Diet: Algae wafers, softened vegetables, small invertebrates.

Clown Plec Panaque maccus
Often referred to by retailers and in older aquarium books as Peckoltia vittata, a different and rarely traded species. Sometimes retailers will list the Clown Plec using the L-number system, in which case this species is known as either L104, L162, or LDA22. Body colour is woody-brown with pale stripes. Closely related to the jumbo Royal Plecs kept by advanced aquarists, this little catfish is hardy and adaptable, but is strongly herbivorous and needs a regular supply of plant foods to stay healthy. It may also eat wood, and bogwood roots must be part of the aquarium. Unfortunately, this species will sometimes nibble on plant leaves, particularly those with stiff leaves that can support its weight, such as Amazon swords and Anubias spp. Water chemistry: 2-20 degrees dH, pH 6.0-8.0. Temperature: 24-28 C/74-82 F. Diet: Algae wafers, softened vegetables, small invertebrates.

Common Plec Pterygoplichthys sp.
This species is of questionable value to most aquarists, getting far too large for their community tanks. Territorial but rarely aggressive except towards other suckermouth catfish, singletons can work well alongside medium-sized barbs, characins, rainbowfish, etc., given sufficient space. Very messy though; a bit filter is essential. Doesn't really eat as much algae as is often supposed; primarily an opportunistic omnivore with a taste for carrion and small invertebrates as well as algae. Water chemistry: 2-20 degrees dH, pH 6.0-8.0. Temperature: 22-28 C/72-82 F. Diet: Algae wafers, softened vegetables, small invertebrates, chunky seafood.

Loaches

Relatively few loaches are happy in hard water, though some of the hardier species may adapt without problems. As with catfish, it's important to ensure loaches get enough food to eat. Loaches are notorious jumpers, and therefore not suitable for open-topped aquaria. Loaches can also be a bit feisty, so choose tankmates with care.

Horseface Loach Acantopsis choirorhynchos
This eel-like loach needs to be kept in a tank with a soft, sandy substrate (smooth silica sand or pool filter sand are ideal) because it is a burrowing species. If it can, it'll bury itself almost completely, with just its head boking above the sand! Needless to say, it will uproot small plants. Maximum length in the wild is 30 cm/12 inches, but 18 cm/7 inches is more usual under aquarium conditions. Not fussy about water chemistry, and can even tolerate slightly brackish conditions,Â but does need clean water with lots of oxygen, as well as sufficient space and sand for digging. Fairly peaceful by loach standards, but a lookalike species, Acantopsis octoactinotos, is rather snappier and reputed to be more predatory towards small tankmates as well. The two species are hard to tell apart, but whereas Acantopsis octoactinotos has a snout that is more or less straight along the top, Acantopsis choirorhynchos has a snout that bends downwards about halfway along, giving the fish a more curved profile. Water chemistry: 2-20 degrees dH, pH 6.0-8.0. Temperature: 22-28 C/72-82 F. Diet: Catfish pellets, algae wafers and live or wet-frozen invertebrates such as bloodworms.

Yoyo Loach Botia almorhae
Probably the best of the Botia-type loaches, this gregarious species needs to be kept in groups of five or more specimens. Usually silvery-gold in colour with brown, approximately vertical bands on its flanks, but these markings are very variable. Not completely peaceful, but if kept in sufficient numbers will generally ignore its tankmates. Maximum length is about 12 cm/5 inches. There are no obvious differences between the sexes. Water chemistry: 2-20 degrees dH, pH 6.0-8.0. Temperature: 22-28 C/72-82 F. Diet: Catfish pellets, algae wafers and live or wet-frozen invertebrates such as bloodworms.

Livebearers

Almost all the Central American livebearers are adapted to hard water conditions, making them the fish of choice for hard water communities. The 'big four' livebearers of the hobby are Guppies, Mollies, Platies and Swordtails, but there are lots of other species besides. Males tend to be quite aggressive, and will fight amongst themselves and bully females, so if kept in mixed-sex groups, keep at least two females per male.

Blue Limia Limia melanogaster
Males of the wild-type fish are greenish-grey with black and yellow spots on their flanks and fins, but a variety with metallic blue speckles on its flanks is now regularly traded. Females are larger (to 6 cm/2.4 inches) but less colourful than the males (to 4 cm/1.8 inches). Enjoys slightly brackish water but adapts to hard freshwater well. May hybridise with Poecilia species as well as other Limia species, so best not to keep them together. Water chemistry: 15-25 degrees dH, pH 7.5-8.5. Temperature: 24-28 C/75-82 F. Diet: Algae-based flake food and small live or wet-frozen invertebrates.

Endler Guppy Poecilia wingei
Smaller and more brightly coloured than the standard Guppy described below, but otherwise very similar in terms of care. The two species should not be kept together because they hybridise readily. May be kept in slightly brackish water if desired. Water chemistry: 10-25 degrees dH, pH 7.0-8.0. Temperature: 24-28 C/75-82 F. Diet: Algae-based flake food and small live or wet-frozen invertebrates.

Guppy Poecilia reticulata
This species is very popular, but the colourful fancy varieties widely sold are not very hardy. If water quality isn't good, they quickly succumb to finrot and fungal infections. So-called Feeder Guppies are closer to the wild-type Guppy in terms of appearance and hardiness. Can be excellent community fish, but males are prone to having their long fins nipped by boisterous tankmates such as barbs. Needs a reasonably large aquarium, 60 litres/15 gallons or more. Arguably more disease-resistant when kept in slightly brackish water, but can be kept in freshwater if environmental conditions are good. Water chemistry: 10-25 degrees dH, pH 7.0-8.0. Temperature: 24-28 C/75-82 F. Diet: Algae-based flake food and small live or wet-frozen invertebrates.

Humpbacked Limia Limia nigrofasciata
Although both sexes are honey-gold in colour with purple vertical stripes, males have speckled sailfins and a more humped appearance than the females. Females get to about 5 cm/2 inches in length, males a little less. Omnivorous and easy to keep, and an excellent community tank species. May be kept in freshwater or slightly brackish water. May hybridise with Poecilia species as well as other Limia species, so best not to keep them together. Water chemistry: 15-25 degrees dH, pH 7.5-8.5. Temperature: 24-28 C/75-82 F. Diet: Algae-based flake food and small live or wet-frozen invertebrates.

Knife Livebearer Alfaro cultratus
This gentle livebearer gets to about 7.5 cm/3 inches in length and is mostly silvery-grey in colour except for patches of blue scales on its flanks. The fins are yellowy. Males and females look quite similar, but males have a peculiarly knife-like edge to the region between the anal fin and tail fin. They also tend to be a bit more strongly coloured. Although the fish itself is hardy and easy to keep, it is one of the more difficult livebearers to breed because the fry are rather small. Water chemistry: 10-25 degrees dH, pH 7.0-8.0. Temperature: 24-28 C/75-82 F. Diet: Algae-based flake food and small live or wet-frozen invertebrates.

Molly Poecilia spp.
Several types of Molly are traded, though Black Mollies and Sailfin Mollies are particularly popular. All can be hardy when kept properly, but they are easily stressed by poor water quality and the wrong water chemistry. On the whole best kept in slightly brackish water, but if kept in plain freshwater conditions, it is crucial that the water is very hard and alkaline, and that water quality is excellent (zero ammonia and nitrite, and nitrate levels less than 20 mg/l). Adult size varies; typically around 8 cm/3 inches, but may be up to 15 cm/6 inches in the case of the larger Sailfin varieties. Males can be surprisingly aggressive. Aquarium needs to be quite spacious, at least 90 cm/36 inches long. Water chemistry: 15-30 degrees dH, pH 7.0-8.5. Temperature: 24-28 C/75-82 F. Diet: Primarily algae-based flake foods, with meaty foods such as bloodworms and brine shrimp used sparingly.

Platy Xiphophorus maculatus
Platies prefer cooler conditions than most other livebearers, so tankmates will need to be chosen with care. Otherwise one of the easier livebearers to keep, and normally a good community tank resident. Water chemistry: 10-20 degrees dH, pH 7.0-8.0. Temperature: 22-25 C/72-77 F. Diet: Algae-based flake food and small live or wet-frozen invertebrates.

Swordtail Xiphophorus helleri
Swordtails come from cool, fast-flowing streams and appreciate tanks that are not too warm and have lots of water current. Swimming space is also very important, and these fish should not be kept in tanks less than 90 cm/36 inches long. Males can be very aggressive. Males get to about 8 cm/3 inches in length, females up to 10 cm/4 inches. Water chemistry: 10-20 degrees dH, pH 7.0-8.0. Temperature: 22-25 C/72-77 F. Diet: Algae-based flake food and small live or wet-frozen invertebrates.

Close

Apart from some restrictions with regard to water temperature and social behaviour, all the fish listed in this article should get along in an aquarium of adequate size. As should be obvious, the range of fish that tolerate or prefer hard water is much greater than many suppose. By choosing fish that'll do well in your water chemistry, you should find your fishkeeping easier and more rewarding than would otherwise be the case.

community tank options; hard water; species 11/23/11
Hi,
<Salve!>
I am not very new to this site, I have been researching different things on this great site for a while. I've had a medium black skirt tetra tank and medium goldfish tank before so I know the basics in tank maintenance. This time I want a more advanced community tank, I want to get my dream 75-90 gal.
<A nice size. Perfect for a big collection of small fish, ideally a few really big schools of fish, so each species looks its best.>
It will have Eco-Complete substrate with low to medium light plants with medium lighting. With the fish, there are some problems.
<Indeed.>
One is compatibility.
<Correct. And also temperature, water chemistry, and water current differences.>
For the species I like, some are compatible with some, but for the rest, I have either not found any information at all or completely different info each time.
<Actually surprised by this last statement. For most of these species, their requirements are actually pretty clear.>
I know for sure I want platies and Cory catfish.
<An excellent combination. Both are low-end tropicals best between 22-25 C/72-77 F, and Corydoras usually tolerate the moderately hard water Platies demand. So no real issues here.>
Here is a list of possible fish-the ones with * are my favorites-and I know several WILL be ruled out:
<Quite so.>
-*All male or female Platies (don't want 100s of fry taking over my tank with livebearers)
- All male Swordtails
<I would keep one species or the other. Platies dislike strong currents; Swordtails prefer strong currents. Look at their body shapes! One is stocky and dumpy-looking, the other streamlined and capable of swimming very fast.
Plus, Swordtails do tend to be aggressive, so if you keep them, it's best to build your community around species able to avoid trouble or at least not cause trouble. Platies do neither, being slow-moving fish that look so like Swordtails that male Swordtails treat them as either threats (males) or potential mates (females).>
-*3-4 species of Cories (Some combo of Leopard, Albino, Bronze, Bandit, Sterba's, Panda, Peppered)
<Of these, Corydoras sterbai is exceptional in being a "hothouse flower" best kept between 25-28 C/77-82 F. So if you go for the low-end tropical situation that you'd probably find best for most of your fish, I'd leave it out the mix. On the other hand, Leopard, Peppered, Bronze and Panda Corydoras make a nice selection of fish with similar requirements.
Honestly, I'd leave out the Albino versions because they look so unnatural, so why include them in a big, planted tank you're taking such care to design properly? Do also check any substrate choices. CaribSea generally don't recommend Eco Complete or Tahitian Moon Sand with "soft bellied" fish such as Corydoras that are prone to having their barbels damaged. Some folks have kept Corydoras in tanks with these substrates just fine. But I'd never recommend it, especially when there are cheaper, safer alternatives like smooth silver sand ('pool filter sand') that work so well. So far as plants are concerned, it doesn't matter what sort of sand you use really; any sand is better than gravel, and if your use a liquid or pellet fertiliser, all sand types can work just fine.>
-*Black neon Tetras
<A nice fish.>
- Silver tip Tetras
<Another excellent fish, but can occasionally be nippy, so be careful with really stupid slow-moving fish like Bettas and Guppies.>
-*3 pearl Gouramis (1 male/2 female)
<An excellent species, but like all gouramis, does prefer slightly warmer than average conditions, at least 25 C/77 F.>
-*1 or 3 Honey Gouramis (don't know if to put 1 m/f or 1 m/2f with Pearls)
<I'd skip these; very shy, so you wouldn't see them, and likely to be bullied by the Pearl Gouramis. Can be fussy about water chemistry, too.>
-*Harlequin Rasboras
<A good species, fairly adaptable, but dislikes hard water.>
- White Cloud Minnow
-*Gold White Cloud Minnow
<These both do best at the low-end of the temperature range, like the Corydoras and Platies, so choose tankmates accordingly. On the other hand, a school of 30 specimens in a tank this size would be lovely! Look out for the STUNNING Vietnamese Cardinal Minnow, a sister species of the White Cloud, but with even BETTER colours. Again, a subtropical fish that shouldn't be kept too warm.>
- 1 or 2 species of Danio (Leopard, Celestial Pearl, Zebra, Gold Zebra)
<Don't keep Zebra and other large Danios with White Clouds, as the poor White Clouds will be harassed to death. Celestials should be okay, but they're questionable community fish given their tiny size, and I wouldn't bother in a tank this big.>
- Several male fancy Guppies (to prevent fighting)
<Nope, I honestly don't think these would be a wise choice here. Delicate, often introduce diseases, prone to damage from other fish, and easily nipped even by generally harmless species like Danios and Silvertips.>
- 8 Tiger Barbs (likely to get ruled out)
-*Gold Barbs (not much info on compatibility)
<Agree, both these barbs would be outstanding choices if the only schooling fish, and perhaps alongside Zebra Danios and Silvertips, but they're otherwise too pushy and aggressive to keep with smaller fish (like the Minnows) or slow-moving fish (like the Guppies and Gouramis).>
-*All male Endler's Livebearer
<See above. Truly, a species for the single-species set up, or else with certain hard water bottom dwellers, like Shell-Dweller Tanganyikan cichlids.>
- Sarpea tetra
<Serpae Tetras are notorious fin-nippers.>
- Flame Tetra
<Not normally a fin-nipper, but approach any Hyphessobrycon species with caution when choosing community tank residents. A gorgeous fish though, and looks AMAZING in shady, well-planted soft water set-ups.>
- Lemon tetra (very nice, but not much info on them)
<A lovely species, and very colourful in shady tanks with soft, slightly acidic water, but often lacklustre in generic community tanks where the water chemistry is wrong and there's too much overhead lighting.>
- Marbled Hatchet (I know about them jumping)
<They're also rather delicate and small, and can be difficult to feed if kept with fast-moving surface fish such as Zebra Danios. The bigger Silver Hatchetfish is to some degree a better community fish, but I'd still get them settled in first, and perhaps avoid any surface-swimming fish except the slowest, most docile types.>
- Ghost or Cherry Shrimp (more optional)
<With very small fish, like the White Clouds, as well as Corydoras, Cherry Shrimps can work exceptionally well, even breeding. But in more boisterous set-ups, they may end up hiding, damaged, or simply eaten.>
- Trumpet Snail or 2 (to aerate substrate)
<I'd skip these if you can get something that breeds more slowly, for example Tylomelania snails or Clea helena "assassin snails". Both of these do just as good a job, but breed at a fraction of the speed. The Tylomelania also get rather big, 10 cm/4 inches in the case of some species, making them impressive pet animals in their own right.>
Tetras, Barbs, Guppies, Hatchets, Minnows, Danios, and Cories will be kept in >7 schools if they make the list. Which ones don't belong in this list because of compatibility, water requirements, aggression/nippiness, etc?
For Tiger Barbs, I know it depends on their personality, but in a med-large school with a large tank and many plants, could they be OK.Same for Danios?
<See above.>
My second problem is that i live in San Diego with its "liquid rock" tap water as many sites say. I feel discouraged to set up a tank because I've read that many of these fish prefer and thrive in soft/acidic water.
<Indeed. Some of your fish are hard water fish anyway, e.g., Platies.
Others are largely indifferent, e.g., Minnows and Corydoras. Relatively few tetras are able to do really well in hard water, but Silvertips are among them. Here are some further thoughts and options:
http://www.wetwebmedia.com/fwsubwebindex/HardWatrCommTkStkMonks.htm
For the most part, your fish will adapt to hard water, but as stated above, Harlequins, Honey Gouramis, and Lemon Tetras are fish that may survive but rarely look their best in hard water.>
Many LFS's here have RO water, which is not an option for me right now, nor is buying gallons of it at LFS's. I've read about acclimating fish, but I don't know if this water is too extreme for more delicate fish like Cories,
<Not delicate at all.>
Celestial Pearl Danio,
<Doesn't mind hard water much.>
some Tetras and Guppies. Do you think it's possible to do this? Also, I don't want to "experiment" with fish and see if they will work out- I'd rather leave them perfectly fine at the store. Many sites suggest setting up a Malawi Lake cichlid tank, though they are beautiful, I don't think I'd be able to handle their care and aggression.
<Indeed, and they'll wreck plants so don't make for "pretty" community tanks. On the other hand, it IS possible to mix some Tanganyikan cichlids into planted community tanks. Julidochromis ornatus for example is a lovely, if shy, Tanganyikan cichlid that doesn't damage plants. It can get along well with midwater community fish, though it can sometimes be a bit hard on Corydoras and other bottom-dwellers if it feels threatened. Given space though, and a few caves to call home, it'd be a definite option.>
What do you think I should do or put into my tank? Sorry for the long message, I tried to make it short as possible.
Thanks so much in advance!,
Tanya

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