Parasites, Pathogens, and Problem
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Ways to protect your pond from -
by Rich Sacher, Louisiana USA
I just love it when I find a new aquatic plant to try in my
pond . . . dont you? Maybe you know a plant as a land plant,
but someone tells you it also grows in water. Or, perhaps a friend
offers you an aquatic plant you have never grown. Or it may be
an intriguing oddity that you discover in a catalogue or on the
internet. In the excitement of your new discovery, you might
practice neither prudence nor patience before acquiring this
freshly desired object and placing it in your pond.
The advice offered here is specifically for you who have garden
ponds which are formed by a liner or concrete shell. Those who
have a one- or two-acre earth-bottom pond are dealing with a
much more complex ecosystem. They should consult their local
agricultural extension agent before introducing any living thing
to their earth-bottom pond; once a plant or animal becomes well
established, it may be costly or impossible to eradicate if it
later becomes a problem. But with a smaller garden pond contained
by its liner, you can dispose of the disaster, even if it means
making the drastic decision to empty the pond and start over.
Here are some cautionary controls that you should be aware
of, to prevent catastrophe in your pond . . . and beyond!
Countless parasites exist that can infect the fish in your
pond; and the easiest way to obtain parasites is to bring plants
or fish from the wild into your aquatic paradise. You may have
expensive koi, or just gorgeous goldfish, but both are susceptible
to anchor worm and fish lice. It may tempting to collect water
hyacinth, pickerel rush, horsetail, etc., and bring them home
to augment your aquatic plant collection. The roots of these
plants can easily harbor parasites, fish eggs, snails, crawfish,
and other critters that do not belong in your pond. Bog plants
may also be infested with caterpillars or spider mites. A single
water hyacinth with spider mites can blow around your pond and
infest other susceptible plants such as cattails, taro, pickerel
rush , cannas, calla lilies, etc.
You are much safer to exchange plants or fish with fellow
pond keepers whose ponds you know are parasite free. (Make sure
THEY dont collect plants from the wild! Ask them!) Some
aquatic and bog plants in the wild are protected species, so
that is another reason to leave them where nature put them. However,
if prudence cannot persuade you to stop digging at the edge of
that native pond, at least promise to quarantine your purloined
plants when you get them home. Keep them in water containers
away from the pond, and grow them this way for the season while
you inspect them often for unwanted hitchhikers. Experienced
fish fanciers quarantine their new fish and observe them for
at least a month before introducing them to the pond. I highly
recommend this excellent practice, whether obtaining fish or
plants from a fellow hobbyist, an unfamiliar store, or though
a mail order company.
Fish are susceptible to pathogens too numerous to name. Various
fungi, bacteria, and viruses can infect fish. Some pond keepers
never seem to have a problem, while others constantly have trouble.
If you overcrowd a pond with fish, overfeed the fish, have poor
water quality, your fish will be severely stressed. Bad things
surely will happen.
Do not overload your pond with fish. In his book "Goldfish
Pool, Waterlilies & Tropical Fishes", Dr. G.L. Thomas
suggests a minimum of 20 square inches of surface area for each
inch of fish in the pond. Circulate and aerate the water with
a pump . . . either through a fountain jet or a waterfall. Use
a biological filter or keep an abundance of underwater grasses
in the pond; one bunch for each square foot of surface area is
the common recommendation. Anacharis, Cabomba and
hornwort are the most popular choices. (If you have koi, they
will eat the grasses...so a biological filter can take the place
of the grasses.) Both absorb excess nutrients. Clear, oxygenated
water helps greatly in keeping fish healthy. Healthy fish tend
to have greater resistance to these pathogens. Beware of accepting
free fish from someone who has too many, unless you
are willing to quarantine them for at least a month to be sure
they are disease free.
If your fish come down with parasites or a disease, you need
to consult an expert for a diagnosis. Once you know the ailment,
use a treatment sold to remedy the problem. You also need to
decide if you are going to treat the whole pond or if you are
going to capture the fish and hold them in treatment tanks until
they are free of what ailes them. (There are 7.5 gallons in each
cubic foot of water.) Either way, you're facing lots of work.
As always, an ounce of prevention is worth a pound of cure!
The internet has truly transformed us into a global village.
Plants from around the world can be ours with a few strokes of
the keyboard and a click of the mouse. And a credit card number,
of course. Buying foreign plants online is wonderful, exciting,
and dangerous! Buying a pig in a poke is always risky, because
you never know what you will get . . . and with aquatic plants,
it could be a whole lot of trouble. Consider the legalities involved:
if you buy a water hyacinth in New Jersey, it may only cost you
$5.00. If you sell it in Florida, it could cost you a hefty fine!
A desirable aquatic plant in one part of the country may be a
noxious and illegal weed elsewhere. Of course, this applies to
exotic terrestrial plants, too.
How can any of us keep up with which plants are legal in which
states? Do we have a license to bring plants into the country?
Or into our state? Could any of these plants escape our pond
and become a widespread economic and environmental nuisance?
If you have never seen a particular plant, and perhaps do not
even know its name, you ought not take it home and put it in
your pond. Do your research first and be sure you are making
an informed decision. A good place to start is Invaders Database System, Noxious Weeds in the
US and Canada. Other countries will similar resources.
The lovely water hyacinth is a well known example of an exotic
aquatic which has spread out of control in the southern United
States. It chokes many waterways to the point they are no longer
navigable. Today we face another pernicious plant, the newly
introduced floating giant salvinia (which probably escaped someones
aquarium) that thrives in Texas and Louisiana. This illegal (in
the US) South American aquatic grows into a floating mattress
almost a foot thick, killing all plant and animal life beneath
it. Boaters innocently give these hitchhikers a free ride, spreading
them to the next lake or bayou. With no natural predators, it
freely spreads like wildfire wherever it finds water in a favorable-to-it
climate. Surely, none of us in any country wants to be so careless
that we introduce the next aquatic plant scourge to our own part
of the world!
Aquatic plants in the wild may spread easily and unpredictably.
Therefore pond and aquarium keepers find themselves an important
line of defense in preventing the introduction of aquatic weeds
into our environment. Along with a passion for our hobby comes
the responsibility to know that the plants we grow are safe and
legal where we live. So, be kind to Mother Earth . . . promise
her that you will never release unwanted plants into the wild.
Use them for a plant swap, donate them to a botanic garden .
. . or put them in your compost pile!