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  • How is the Native Freshwater Aquarium Different?


    Going native opens up a whole new range of species, communities and aquarium styles to the fish keeper. Some of the fish may seem familiar – anyone who knows gobies or triplefins will instantly recognise the native bullies – while other species are totally unique. The different habitats that these fish occur in leads to entirely new aquascapes or biotope options. Furthermore, the aquarium keeper can actually visit the streams that these fish live in, catch the fish themselves and even model their aquarium on distinct areas of specific streams.

    The most immediate difference from the usual aquarium is that a native aquarium has no plants. For a biotope aquarium, plants are not used simply because native aquatic plants are absent from most waterways. The heavy forest shading or high flows  of New Zealand waterways prevents the plants from establishing. Those that do attempt to use plants soon discover that there aren’t any native algae-eaters to keep them clean and crayfish will uproot or eat most plants. Wood, leaves and ponga fronds can be used instead of plants to provide textural variation.

    The best tank shape for a native aquarium is long, low and wide.  Water depth is not important as most species are found in shallow streams and the edges of rivers. However, ground area is very important for those that spend most of their time on the substrate, while aquarium length is important for larger species and the flighty schooling fish. The aquarium should also be constructed so that the fish cannot jump or climb out (yes, some can climb!). A well-fitting hood, tight lids or European bracing is a must.

    Most of our native species are somewhat secretive and need hiding places. Others use the caves as territories, while those that rarely hide appreciate having the caves available for when they do. It goes against what you would expect, but the more hiding places available, the more the fish will be seen, since they feel secure and able easily to dart to safety from any point in the aquarium. Similarly, lower lighting levels help the fish to feel more secure, and also looks far more natural.

    One feature which is not so visible but it absolutely critical to the success of a native freshwater aquarium is keeping the water cold. This is usually not such a problem over winter, but it can be a big problem in summer. Most fish start to stress in water above 18°C, and the aquarist should become stressed if the aquarium gets above 20°C. Short term temperature spikes can kill by lowering the oxygen, while long term elevated temperatures or fluctuations can affect the fishes’ immune system, leading to disease outbreaks.

    Stopping the aquarium from becoming warm in the first place is far more effective than trying to remove the heat from it. Ensure the aquarium is in a cool and well-ventilated room to begin with, and insulate the non-viewing sides with polystyrene. Use cool, low-wattage lights (preferably LED) and remember that every pump will be adding heat directly to the water, so choose filtration and flow equipment carefully. A much larger volume of water will have a more stable temperature and water quality than a small aquarium, which can be achieved by expanding the total volume of water, by plumbing in a plastic drum or water tank.  For actually cooling the water, a fan aimed at the water surface can help through evaporative cooling, and frozen bottles are handy but laborious, while a chiller is the most effective but also the most expensive.

    Basic Requirements

    • Cold water – not just room temperature, these fish like it cold.
    • Clean water – weekly partial water changes are a must. Healthy water means healthy fish.
    • Lids – all native fish can climb or jump out, even through tiny gaps.
    • Large ground area – horizontal space is far more important to these fish over vertical depth.
    • Hiding places – it seems counter-intuitive, but the more hiding places available the safer they feel, so they come out more.
    • Carnivorous diet – live invertebrate foods are best, though ox heart with the fat removed is a convenient option.
    • Ethical collection – they are wild animals, native to New Zealand, and most are in decline. This must be borne in mind at all times.
    •  Knowledge – really, this is the most important bit. The more you know the more successful you will be at fish-keeping. Don’t stop reading, searching and asking. There are many books, websites and forums out there on general aquarium keeping, and Stella McQueen and R. M. McDowall’s books and articles are essential reading for anyone interested in native fish.


    Native fish species for the Aquarium

    Bullies are really easy to keep and are endlessly entertaining with their territorial behaviours and ability to spawn in the aquarium. These remain my favourite native aquarium fish. They live on and around the substrate, buzzing in and out of rocky crevices and chasing away intruders. They readily spawn in the aquarium. Most grow to around 9 to 10 cm on average, with the smallest species only attaining around 6 cm and the largest capable of reaching over 20 cm.

    Inanga are the most common whitebait species. They grow up to be a slender 8-12cm translucent fish with a silver abdomen, spotted back and occasional flashes of iridescence. They are a very fast-swimming, mid-water shoaling fish, so are best kept in a long tank and in groups.

    Banded kōkopu are another whitebait species, only these grow up to be a fat 20cm fish, and are earthy brown with thin amber stripes. They like a darker, slow-flowing aquarium with large crevices behind rocks or wood to sleep in or lurk behind. They can be a very active and sometimes aggressive fish, with feeding time being a splashy frenzy and often becoming aggressive during the testosterone-fuelled teenage years (2-3 years old). Small kōkopu play well with others but larger ones may need to be separated.

    Kōaro are another whitebait species. Kōaro live in clear, cold and fast-flowing upland or mountain streams and are expert at climbing waterfalls to access these habitats. They are large like the banded kōkopu, typically growing to 16-18 cm, and are a speckled silver-grey. 

    Torrentfish live in very fast flowing, shallow water, hiding under the stones and moving into the quieter areas at night to feed. They are a beautiful although shy aquarium fish and are very sensitive to raised temperatures or poor quality water. They grow to around 13cm and are not aggressive with other fish. An effective cooling system is critical for this species.

    Eels are secretive nocturnal predators. In an aquarium they may hide most of the time (especially when small), or sit very still out in the open. They are escape artists.

    Smelt are a silvery, schooling fish with a very distinctive cucumber smell. In the early stages of capture and acclimation they are unfortunately very prone death through stress. Usually those that survive the initial period will live for several years in the aquarium. Keeping them very cool during this period is helpful.

    Mudfish are a specialist wetland species, able to survive the wetlands drying out over summer by finding damp places under logs and simply waiting for the water to return. They can spend several months out of water as long as they remain damp. Mudfish are under threat due to the extensive and ongoing destruction of their wetland habitats. Only the brown and black mudfish should be considered as they are less threatened. A mudfish aquarium is very easy to look after and is an excellent public educational tool.


    Brown mudfish - This mudfish aquarium has a thick peat substrate overlaid with dense leaf litter, hiding large pieces of wood which the mudfish burrow under. This is the easiest aquarium to maintain. Filters cannot be used as the peat would clog them, but the natural bacterial colonies in the peat ensure excellent water quality. Gravel vacuums cannot be used, so water changes are simple drain-and-fill operations. Periodically the leaf litter needs to be replaced and the peat probed to release gas pockets.

    Crayfish/koura are not a fish but they are a fascinating addition to the native aquarium or make a good pet on their own. They can be very aggressive and should not be kept with other crayfish or fish smaller than themselves, particularly the ground-dwelling bullies. They need plenty of hiding places and a varied diet of vegetables and insects or ox-heart. They grow by shedding their shells – the first time you see a recently shed shell you will probably think your cray has died. They will eat the shell over the following week to recycle the calcium.

    Freshwater mussels/kākahi are frequently sold in pet shops as a living filter, as they feed on particles and microorganisms that they filter from the water. However, it is extremely difficult to provide enough food in an aquarium for them and most will slowly starve to death over a period of months. Mussels are also in severe decline in the wild due to a combination of declining water quality and lack of recruitment of juvenile mussels. As such, mussels should be avoided.

    There are many more species of native fish beyond those listed here. Some have naturally very narrow geographical ranges making them less practical for most people to find. Others are much harder to find as they are sparse in many regions or the species is nationally threatened. Some have only been identified as separate species in recent years and little is known about the population status or habits.

    As always, please research your area before you go hunting and avoid taking any species from the wild that may be nationally or locally threatened, or if you are uncertain of their requirements.



    adult length (average)






    hiding places






    aquarium type





    9-10 cm






    spawning season mainly



    (excl. wetland)




    8-11 cm












    lake, forest, coastal


    banded kōkopu



    20 cm









    age 2-3 years and older









    16-18 cm









    a few can be really nasty









    10-13 cm


















    up to 2m













    (excl. wetland)






    9-11 cm












    lake, forest, coastal






    10 cm


















    7-10 cm









    keep singly




    (excl. wetland)






































    Types of Aquaria

    The most successful aquaria are built around a particular theme. It will look more cohesive and will be easier to look after as all the fish species have similar requirements. You may wish to showcase your favourite fish species or a particular habitat type, such as that found in your favourite stream. From that foundation, explore the habitat characteristics of that species or stream and associated fish species.

    Below are some examples of habitat-based aquaria and the species and construction elements typical of them.

    Forest stream

    • Banded kōkopu, bullies, inanga, smelt, eels, crayfish,
    • Rock/gravel/sand substrate, wood, ponga fronds, leaf litter
    • Tannined water
    • Current is not important
    • Floating plants



    Forest Stream - Natural environments are rarely pristine, and allowing algae to build up on interior surfaces helps to give the aquarium an aged and earthy feel, especially relevant when trying to replicate a forest stream. The algae looks entirely on purpose when the viewing panes are kept clean.


    Forest Stream - The textures of wood, rock and pong a gives variety and depth to this forest stream aquarium. The ponga has the added effect of making the aquarium immediately appearing native, even to those who wouldn’t recognise the fish. Fresh ponga leaves take a few months to turn brown when submerged, and will remain intact for around six months, depending on how gently they are treated during tank maintenance.


    • Torrentfish, kōaro, bluegill bullies
    • Rock/gravel substrate
    • Clear water
    • Strong current
    • No plants or wood, very clean rocks



    Riffle - This riffle aquarium contains an astonishing amount of rocks and gravel. Wood and plants would be washed away in the fast-flowing habitat it is replicating. It looks still but the water is being blasted around by two 3200L/hr pumps, providing variable currents around the aquarium allowing the different riffle species to divide their time between surfing the waves  and sheltering from the storm


    • Smelt, non-migratory bullies, eels, crayfish
    • Fine pebble and sandy substrate
    • Minimal current
    • Emergent reeds, nitella, floating plants
    • Native aquatic plants (if there are no crayfish)

    Coastal stream

    • Specifically giant bullies. Also other bullies, inanga, smelt, eels, crayfish, shrimp
    • Sand and pebbles, driftwood
    • Current is not important
    • Aquatic plants and emergent reeds (if there are no crayfish)


    Lowland - This simple aquarium evoking a coastal stream  and featuring a sandy substrate, few scattered pebbles, plastic ‘rushes’ and a collection of kawakawa branches acting as submerged tree roots, was home to several bullies and a small school of inanga.


    • Mudfish only
    • Peat, dense leaf litter, wood
    • No water flow
    • Nitella and floating plants


    Conservation and Ethics

    Conservation must always be of utmost importance when taking native animals from their natural environment, especially when the wild populations may be threatened or undergoing gradual human-induced decline. Many of these fish are threatened by habitat destruction and degradation. This includes not only the direct piped pollution of rivers, but also the loss of bankside vegetation and forest cover, drainage of wetlands, agricultural nutrient run-off, stock grazing at the water's edge and the construction of dams, weirs or culverts. Introduced species, such as trout (Salmonidae spp.) and mosquitofish (Gambusia affinis), not only compete with native fish for habitat but are known to eat them.

    It is important to know not only the national threat classification of a species, but also its local population status. A species that is fairly widespread and nationally common, may also be locally rare or threatened.

    It is preferable that only juveniles are taken. Young fish not only adapt much easier to the aquarium, but also their disappearance generally has less of an impact on the remaining population. While it is great fun catching the biggest fish in a stream, be impressed at their survival and then leave them behind to help ensure the continuation of the species.

    It is important not to take more fish than you can comfortably house and have the dedication to care for. Take care when considering the release of fish that have had an exclusively non-live or commercial diet, or that have been in captivity for most of their life, as they may struggle to readjust. A diseased fish must never be released into the wild, even if the disease is present in wild populations.



    As these are native animals there are laws restricting what you may and may not do with them.

    Unfortunately these laws were developed in a very ad hoc manner over time. Different aspects are covered by different laws and government departments, sometimes several in conjunction. In some instances old laws were not repealed when a new one was enacted.

    Advice received from the Department of Conservation (DOC) suggests these general guidelines:

    • A permit is not required to keep native fish and crayfish in aquaria.
    • There are restrictions on taking aquatic life from conservation lands (national parks and reserves etc) and this requires a permit from DOC.
    • Whitebait may only be taken in accordance with whitebaiting regulations (pamphlets outlining these are readily available from DOC offices or on their website).
    • Anyone may take eels for non-commercial purposes, within the daily bag limit of 6.
    • Anyone may take freshwater crayfish for non-commercial purposes, within the daily bag limit of 50.
    • Black flounder are part of the managed commercial and recreational flatfish fishery and there are regulations which apply to anyone taking these fish for any reason, including the home aquarist. Both the minimum legal size and the cost of a permit to take undersized fish basically excludes this species from aquaria.
    • Only the local iwi may take crayfish or native fish from the Lake Taupo or Lake Rotoaria catchments.
    • A permit is required to release a native fish into a waterway, even if it came from there originally. This is partly to prevent the introduction or spread of disease. This permit can be obtained from the fisheries division of the Ministry of Primary Industries (MPI).
    • A permit is required to transfer aquatic life (fish, plants, invertebrates etc) from one natural waterway to another. If the species does not exist in the recipient waterway DOC permission is required. If it does already exist there, approval is required from MPI.
    • Moving aquatic life between the North and South Islands requires approval from both the MPI and DOC.
    • Licenses are required for the farming or sale of native fish and crayfish, for food or the pet trade. However any person may sell legally-caught whitebait.

    This is a very basic and generalised guideline and should not be considered as legal advice. For further information please contact your local DOC office.

    Remember the laws are not there purely to restrict private ownership and commercial activity, but to ensure the survival of the species and their natural distribution and local genetic variations. They should be adhered to for conservation concerns as much as, if not more so, than simply not breaking the law. While some of the laws sound minor or picky, they are enforced.


    Recommended Reading


    Coffey, B.T. & Clayton, J.S. (1988). New Zealand Waterplants: A Guide to Plants Found in New Zealand. Hamilton, Ruakura Agriculture Centre.

    Jones, J. (2005). New Zealand Wild: Freshwater Eels. Auckland, Reed. 40pp  (this is a children's book but an excellent introduction to native eels)

    McDowall, R.M. (1990). New Zealand Freshwater Fishes; A Natural History and Guide. Auckland, Heineman Reed. 553pp.

    McDowall, R.M. (2000). The Reed Field Guide to New Zealand Freshwater Fishes. Auckland, Reed. 224pp.

    McQueen, S.L. (2010). The New Zealand Native Aquarium. Palmerston North, Wet Sock Publications. 126pp.

    McQueen, S. & Morris, R. (2013). A Photographic Guide To Freshwater Fishes of New Zealand. Auckland, New Holland. 143pp



    New Zealand Native Fish – Facebook page  www.facebook.com/nznativefish

    A Facebook page devoted to sharing articles and research relating to native fish, and the fishy photos and experiences of Stella McQueen working in the field.

    Te Ara: Encyclopaedia of New Zealand, Freshwater Fish Section  http://www.teara.govt.nz/en/freshwater-fish

    Some good basic introductions for many native fish. The photographs are amazing and there are also some incredible short videos.

    NIWA Fish Atlas  http://www.niwa.co.nz/freshwater-and-estuaries/nzffd/NIWA-fish-atlas

    Very useful overviews of all New Zealand freshwater fish, including introduced species. The distribution maps are invaluable.

    NIWA Quick-Guides to Freshwater Flora and Fauna  http://www.niwa.co.nz/freshwater-and-estuaries/management-tools/identification-guides-and-fact-sheets

    A fascinating set of flow-charts for identifying different aquatic organisms, including invertebrates, fish, plants and algae. More aimed at the scientist than the layman, and the fish are based on dead specimens, but fascinating nonetheless

    Crayfish World   www.crayfishworld.com/contents.htm

    An Australian site and therefore focused on Australian species, but it does contain some interesting information and photographs, particularly the pages about moulting, sexing and reproduction.

    There is quite a trade in crayfish species for the aquarium market in different parts of the world. While these sites tend not to include our native crayfish, much useful information may be gleaned about crayfish in general.

    Waitakere Regional Council  www.waitakere.govt.nz/abtcit/ei/ecowtr/frshwtrfsh/frshwater-fish.asp

    The usual brief descriptions of the common species, but also includes several short videos and unique photographs of a few species.


    YouTube Videos

    www.youtube.com/nznativefish  Some of my videos of native fish in the wild and in aquaria.


    Useful Scientific Papers Online

    Observations on Growth and Behaviour of Galaxiidae in Aquaria  www.nzetc.org/tm/scholarly/tei-Bio17Tuat01-t1-body-d6.html

    A very interesting article by freshwater fish scientist G.A. Eldon detailing his experiences keeping various galaxiids.

    Taking the fish to the people  https://www.academia.edu/1421445/Taking_the_Fish_to_the_People_-_a_guide_to_creating_successful_public_native_aquaria

    A guide to designing a successful native aquarium for public display and education. Written as an adjunct to the book The New Zealand Native Freshwater Aquarium by Stella McQueen.

    Conservation status of New Zealand freshwater fish, 2013.  http://doc.govt.nz/Documents/science-and-technical/nztcs7entire.pdf

    The latest threat classification of freshwater fishes in New Zealand.


    S L McQueen


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