Pondkeepers love assorted varieties of goldfish
and koi. Now ponders are discovering that other fascinating fishes
thrive in their ponds. Besides the expected cold-water types,
tropical and semi-tropical fishes can thrive in temperate climate
Koi (Cyprinus carpio) and sailfin mollies
Fish for Your Pond
by David Smith, England
Click images to enlarge
All carp, and many other fresh water fishes, belong to the
order Cyprinidae. Carp varieties include the well-known
koi (Cyprinus carpio) and the goldfish varieties from
the common goldfish (Carasius auratus) to all fancy varieties
bred from it. These include the shubunkin, pearlscale, oranda,
lionhead, black moor, comet, and others. Many of these fish can
be kept outdoors in England and other temperate climate areas
throughout the winter even when some ice forms on the water.
However, the more fancy varieties like pearlscale, oranda, lionhead,
and black moor appreciate not being subjected to more than an
occasional day of ice coverage.
If the pond has a very deep area, so much the better so the
fish can descend to the bottom during severe weather. Some koi
keepers recommend a pond as deep as six metres (seven feet) to
encourage deep body growth. A friend of mine keeps his koi in
a pond of 1.3 metres (four feet) plus, a satisfactory depth.
Most koi enthusiasts in England never use plants (including waterlilies).
They maintain their ponds using powerful pumps to provide a constant
exchange of water through vast containers filled with a variety
of filtering media. Although I know many of you who keep koi
with your lilies, I hear of many instances of the waterlilies
being seriously disturbed by the koi rooting the plants out of
their pots. Goldfish varieties do not reach the size of koi and,
although they enjoy rummaging around plants (and eating them),
they are not a threat to established lilies. Koi, remember, can
reach almost a metre (three feet) long in some circumstances.
The cold-water sturgeon (Acipenser sp.) is becoming
popular in English home ponds. The splendid site www.sturgeon-web.co.uk offers all the information
you would ever need about these fascinating fish. This supplier
and expert of the species is in England, but if you are non-English
and wish to acquire sturgeon, I am sure suppliers operate in
Pondkeepers fortunate enough to reside in a more temperate
zone (winters without day-long ice coverage) find that they can
keep a variety of tropical and semi-tropical fish out of doors
throughout the seasons. This happens in the wild, too. Reportedly,
non-indigenous fish species have been introduced into Florida
lakes and have become a nuisance.
The Oscar (Astronotus ocellatus), for example, has
become well established and, being an aggressive big fish, seriously
threatens some of the species natural to the state. Such a fish,
when full grown, may well disturb planted lilies.
I keep many of my favourite fish species in a heated
greenhouse pond. These include archer fish (Toxotes jaculatrix),
uaru cichlid (Uaru amphiacanthoides), silver dollar (Metynnis)
which have bred in the pond, zebra (Danio rerio) which
breed frequently, lace gouramies (Trichogaster leeri),
cardinal tetras (Paracheirodon axelrodii), plecostomus
catfish species (Hypostomus plecostomus), and even discus
(Symphysodon aequifasciatus). All of these thrive extremely
However, I emphasize that the pond is kept never knowingly
lower than 80F (27C) degrees. It does descend to around 75F (24C)
degrees and the stock could stand 70F (21C) degrees, but uaru
and especially discus would not enjoy too long as low as that.
With the exception of lace gouramis and zebras, most of the others
require soft acid water (discus and uarus in particular), and
for this I use both rainwater and RO (reverse osmosis) water.
The archer fish, although a lover of brackish water, tolerates
fresh water. It's great fun to see them fire water at flies and
other insects, mostly swimming near the surface of the water.
They can jump out of the water and end up as dried fish on the
Only experienced aquarists should consider keeping discus
because their water conditions and other needs must be strictly
monitored; and they're quite expensive fish to buy.
Archer fish (Toxotes jaculatrix)
Image from Akwa Foto.pl
Lace gourami (Trichogaster leeri)
Image from Home.no
Zebra (Danio rerio)
Image from Fishbase.org
Mosquitofish (Gambusia affinis)
Image from Bishop Museum.org
If I lived in Florida, I would grow tropical fishes outdoors
and keep a pond heater set at 75F (24C) degrees in case the air
temperature drops too low. The alternative would be to restrict
the inhabitants to those who can stand a wider range of temperature.
Mosquitofish (Gambusia affinis) are native to the mild
winter climate of southeastern portions of the United States.
Introduced into California as early as 1922, they are one of
the most effective non-insecticidal, non-chemical methods of
Being viviparous, they require no special environment (as most
other fish do) for depositing and hatching their eggs. At about
six week intervals throughout the summer, they produce 50 to
100 babies per single brood. The young measure approximately
a half centimetre (a quarter inch) in length when born and grow
to a maximum size of about seven and a half centimeters (three
inches). They begin the work of destroying mosquito larvae at
once. Mosquitofish can eat mosquito larvae as fast as the larvae
hatch from eggs, as many as 100 per day. The early brood born
in April and May begin reproducing when six to eight weeks old.
Mosquitofish live two to three years and tolerate a wide range
Swordtail (Xiphophorus helleri)
Image from AquaBase.org
You can keep many aquarium fish varieties in a pond wherever
in the world you find a favorable temperature range. Some varieties
can live in a wide variety of water temperatures and are quite
hardy. The viviparous swordtail (Xiphophorus helleri),
both in the well-known red form and colour variations, are very
hardy and fast swimming.
Paradise fish (Macropodus opercularis) sport a gorgeous
mixture of reds, blues, and pale yellow. They withstand a very
wide rage of temperature from as low as 50F (10C) degrees up
to being comfortable at 90F (32C) degrees, and live for up to
A bubble nest builder like bettas (Betta splendens), also
known as Siamese fighting fish, can be aggressive toward smaller
fish. Although the males fight within the confines of an aquarium,
they seldom fight in a pond offering so much more room and many
hiding places. The advantage of these is that you can also keep
other plants, such as Cabomba and Ludwigia with them without
plants being eaten as in the case with koi and goldfish. At the
water surface the plants produce pretty flowers which become
an attractive foil for the flowers of our waterlilies.
Image from Atlas Dr. Pez.org
Another excellent and gorgeous range of fishes that may be kept
at a wide range of temperatures should be quite well known to
many of you. These are the sunfishes Lepomis megalotis
and Lepomis gibbosus (pumpkinseed sunfish). The pumpkinseed
is regarded as a nuisance and is banned in some places. Both
are aggressive fishes and should only be kept with larger species
because they grow to 15 to 20 centimeters (6 to 8 inches). Other
sunfish are the Enneacanthus species such as gloriosus.
Many other sunfish make be good inhabitants for your ponds.
W. Sneegas - Animal Diversity.org
In conclusion, I find that many interesting varieties of fishes
can be kept in the warmer ponds. If your pond is in a much colder
zone, you would be better off keeping the cold water species.
Of course, many types of these cold-water fish are extremely
common, such as dace, tench, rudd, common and mirror carp, and
not particularly colourful.
Great Fish Links -
Read these terrific fish articles
Tropical Fish in the Water Garden Vol.
4.2 | Goldfish Varieties Defined Vol.4.3
Finnage in Goldfish Vol.
The how and where of Buying Koi Vol.
2.3 | The Koi Pond in Spring Vol.
All Koi Are Not Created Equal! Vol.
3.4 | Identify the many varieties of Koi - Sanke Vol.
Koi Varieties - Showa Vol.4.3
Koi Clubs of America | KoiVet.com
Check List of Florida's Freshwater Fishes, with
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