The right fish for your aquarium
From the over 30,000 fish species of the world in fresh and marine water only a tiny part is regularly kept in aquariums. Since an animal species has never been wiped out by pet keeping and not even the world’s most caught aquarium fish, the cardinal tetra, has ever been endangered in its stock by its millionfold capture (stock figures in nature unchanged for decades), we shouldn’t feel guilty about keeping fish in aquariums. More and more fish and invertebrate species have been bred, so that there is no need to remove them from their natural habitats. Unfortunately some fish species exist only in aquariums because their natural habitats have been destroyed. In such cases catching aquarium fish can count as active nature conservation, because the fish catchers are helping fishing areas (i.e the habitats) remain intact to secure their livelihood!
We aquarists divide fish in three main groups: freshwater fish, marine fish and brackish water fish, which live in freshwater and marine water biotopes, as well as in the regions in between.
When selecting your aquarium stock please take the following points into account for each fish species:
Is your aquarium large enough? Some sucker catfish (as an example) can become 30 cm long! Are the fish sizes of different species compatible or does one species regard another one as food?
Highly active fish (e.g. rainbow fish) need a lot of space and long aquariums. High-backed fish (e.g. angel fish) need high aquariums.
Way of life
Do your fish (a lot of cichlids, as an example) need hiding places? Do they need wood (as many sucker catfish)? Do they dig and need soft soil (e.g. armoured catfish, loaches)?
Are the fish territory-forming (as are many cichlids)? Do you need to keep them in pairs, in a harem or in a shoal? How well can the fish be socialised with your other fish species?
Do the fish need highly specialised food (e.g. puffer fish often eat ONLY snails)?
Are they plant-eating fish (e.g. long-whiskered cat fish, Leporinus tetras)?
Do the fish have special demands on the water quality (e.g. discus fish prefer pH values below 7.0)?
Do you need to fully cover the aquarium because your fish like jumping?
The most important orders and families in freshwater aquatics
Of course, there are still more families and orders, such as armed spiny eels, Asiatic glassfishes, snakeheads, gobies etc. If you decide to keep one of these fish, please find out what demands the animals have on aquarium size, water, socialisation and food.
We can’t give you any general tips because the demands of the individual families or species vary widely. There are species like the red-tailed black shark which prefer individual keeping or shoal fish, such as most barbels and danionins.
Most tetras are shoal fish and should be kept in groups of 10 minimum. Three fish do NOT make a shoal!
These magnificent and lively fish from Australia are shoal fish which need a lot of space for swimming.
Livebearing tooth carps
Unlike the egg-laying tooth carps they have living babies. Male animals pursue the females aggressively and a harem of females is therefore needed. Note: This great enthusiasm for reproduction means your aquarium dwellers will increase rapidly in number!
Egg-laying tooth carps
Unfortunately they don’t live very long, but is not very difficult to breed them. They often have certain demands on the water quality (hardness, pH value) which also ought to be followed. They love densely planted aquariums.
Almost all species are territory-forming and defend their territories against their own species, often also against other fish. It is interesting to observe the way cichlids care for their brood, but their aggressiveness can make them difficult to keep.
They are very interesting and colourful fish of which many species build floating foam nests.
They are often employed as effective snail eaters. But if they have no snails to eat anymore, they quickly get bored and bite other fish. Many species need a bit of sea salt with increasing age because in their natural habitat they live in brackish water. Some species can ONLY be fed with snails! Often blowfish learn from other socialised fish that granulate or live food can also be quite tasty and start to eat this food, which they would probably not do if they were kept in isolation.
If you decide to keep one of these fish, please find out what demands the animals have on aquarium size, water, socialisation and food.
Brackish water fish
Brackish water fish live in the area between marine water and freshwater. The salinity of the water is therefore a value between that of marine water and freshwater. Although the animals tolerate both extremes (marine water/freshwater) they mostly feel more comfortable in midrange values in the long run. Some species migrate from marine water to freshwater and the other way round. Keeping aquarium plants is impossible because of the salinity. Only mangroves tolerate the required and fluctuating salt concentrations. Fish in brackish water have quite special needs and should only be kept by experienced aquarium owners.
Roots protruding above the water are also welcome. It is important that there is warm air (26-30°C) and the water temperature is between 26 and 28 °C. The salinity may fluctuate, but shouldn’t drop to freshwater level for too long. Although mudskippers prefer live food (including house crickets and worms), they also learn to eat frozen food and dry food ( JBL Krill , JBL NovoArtemio ).
(Many) puffer fish
Only very few species tolerate pure freshwater. Socialisation with other fish may be a problem. Regarding food, they are definitely a bit choosy: live food and snails are first priority for them. Substitute food is difficult, but not impossible. After a learning phase, food tablets attached to the pane ( JBL NovoTab ) are also readily eaten. But you need to feed them snails at regular intervals to wear down their teeth.
All others are brackish water dwellers. They live in small groups and only feed predatory (carnivores). Food: insects (on water surface or in the land part over the water part), small fish and, after habituation, also other live foods.