A Quick Note About Water Quality
We've all been guilty of it at one time or another - but many
pond owners get all stressed out and worked up about adding all
the 'right' chemicals, additives, etc. to their pond, hoping
that it will keep their fish healthier and happier.
Not that there aren't some really good additives out there,
but the bottom line is that if you just focus on keeping your
water quality high, and your pond clean of debris and decaying
organics - you should be in pretty good shape.
Here are the essentials of good water quality:
Oxygen - This is one of the fundamental elements that
many pond owners ignore. Your fish can't breathe air like
we can, so they need a high enough concentration of oxygen in
the water to survive. If you are not aerating your water
sufficiently, for example, by running a waterfall, fountain, or
spitter, then you may be depriving your fish of the precious
oxygen they need to survive.
Especially in the warmer summer months, you need to make sure
that you are aerating your water well enough to keep the oxygen
content high enough for your fish. As the water warms up,
the water actually holds LESS oxygen than at colder
temperatures. If you have lots of fish, or if your pond is
overcrowded, then this can be especially dangerous.
So, just because everything was ok in the springtime - don't
assume that your fish have enough oxygen in July/August when
things really heat up. Summer is a good time to think
about installing an additional fountain or air pump. You
can usually just go down to your local pet shop and pick up a
large aquarium air pump, some airline tubing, and an airstone
and drop that into the pond for some extra oxygen. This is
not practical for larger ponds, but is a great way to aerate
Larger ponds usually have a bigger waterfall, so are usually
ok - but don't be careless and leave your waterfall off during
the hot mid-day hours or you may see your fish gasping for air
at the surface. If you ever do see your fish gasping at
the surface, it's a sure fire sign that they are not getting
enough oxygen from the pond water, and that you need to aerate
your water more.
pH - Fish can live in a wide range of different pH's,
but it's very important to note that sudden changes in pH can be
very stressful for your fish. And also important to know,
is that a 1 point change in pH is actually a 10 TIMES
DIFFERENCE! pH is measured on a logarithmic scale, so the
difference between a pH of 7 and 8 is not just 1 to the fish,
it's 10 times different - so be very careful when raising or
lowering your pH in your pond. You never want to go from a
low pH of 6.5 straight to 7.5 or 8, or vice-versa. This
would be very stressful for the fish, and can even be fatal.
This is also important to keep in mind when doing water
changes, or adding new fish to your pond. Always try to
acclimate your fish to new water, and always test the pH of both
new water and compare it to the old water. Try to make
adjustments to the pH beforehand, or again - acclimate your fish
slowly, over 15 minutes or so. This will prevent
unnecessary stress on your fish.
Ammonia/Nitrite - Some pond owners are still not
aware of the dangers of Ammonia and Nitrite in the pond, and the
potentially deadly effects they can have. Here's a quick
review of the Nitrogen Cycle in your pond.
Fish produce liquid waste in the form of Ammonia, which is
very toxic to fish at higher levels. In an established
pond, and ideally with an established bio-filter, a good
bacteria called Nitrosomas feeds on the Ammonia and breaks it
down into another toxic chemical called Nitrite.
Another beneficial form of bacteria called Nitrobacter, uses
the Nitrite as a food source, and breaks it down into Nitrate,
which is non-toxic and is absorbed by plants or just breaks down
in sunlight. This is the same natural process that occurs
However, in overcrowded ponds, or ponds without a properly
sized biological filter, the levels of Ammonia and Nitrite can
build to dangerous levels. At higher levels, this can
severely stress the fish and can either lead to disease by
weakening the immune system over time, or can cause death by
Ammonia or Nitrite poisoning. Every pond owner should have
an Ammonia and Nitrite test kit, and periodically test for these
We'll get into how to handle high levels of Ammonia and
Nitrite in future articles, but for now just be aware that this
can be dangerous.
Algae - Having too much algae in the pond, especially
green water algae, can be detrimental to the fish because while
algae and plants give off oxygen during the day, they absorb
oxygen during the night - and give off carbon monoxide.
So, if you pond is very green, you can have your dissolved
oxygen levels fall to dangerous levels during the night and
early morning. I've seen complete pond wipe-outs happen
A bad algae bloom and poor aeration caused a massive fish die
off at the Japanese Embassy several years ago. They had
their large waterfall turned off, and the shallow 50,000 pond
had an algae bloom that essentially wiped out half of their 400
They called me over to diagnose the problem, and at first we
couldn't find anything wrong. Ammonia and Nitrite levels
were fine, none of the fish showed any signs of disease - but
when we tested the dissolved oxygen levels of the water, it was
clear that the fish had essentially suffocated overnight as the
suspended algae sucked all of the oxygen out of the water.
Parasites/Bacteria Control - This element really
should not be much of a worry to you if you keep your eye on all
of the other elements above. Fish are like people in that
they always have some parasites and bacteria in or on them (just
like we always carry the common cold), but their immune system
keeps them healthy and disease free.
However, if their immune system is overly stressed, by say
high Ammonia/Nitrite levels, or rapid changes in water
temperature or pH, then their immune system can be affected and
they can get sick.
If you do notice that your fish have obvious growths, or
disease - treat them quickly and aggressively to avoid the other
fish getting sick. You should always have the ability to
set up a hospital or quarantine tank quickly, to isolate sick
Similarly, always try to quarantine new fish, for two weeks
or so, before adding them to your pond. Many pet store
goldfish and koi are so stressed out by being transported, and
by being in over crowded conditions, that it's easy to pick up
some kind of parasite or bacterial infection from adding new
fish to your pond.
But that's really all you have to worry about! By
keeping your pond stable and healthy according to the above
parameters, you should not have any trouble with your pond all
season. No need to buy all those (sometimes) expensive
additives and treatments. Just make sure that you do have
a properly sized filter and a way to aerate the pond, and you
should be just fine...
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