The New Generation of
Beneficial Pond Bacteria
No Harsh Chemicals
Pond Care Treatments
Ponds with Dissolved Oxygen
is obviously essential to fish health, but how much or how little? Two
test kits are available, I would recommend owning one of them. There is
that is in a little vial you break in the water to be tested and collect a blue sample and compare it to a chart.
levels would be 5ppm. This level will permit fish to live a few days.
Levels as low as 3ppm at least partially explain why fish are dying
like flies. Levels as low as 7 could, and should be improved with an
air stone o r Venturi pump. Levels over 8 ppm are desirable, but 11 or
better (up to 14 ppm) are glorious. Low Dissolved Oxygen is an
underestimated cause of fish losses, particularly because of its
synergistic effects with other toxins like Ammonia.
is 'oxygen starvation'. Most koi ponds are usually well served with
venturi returns or waterfalls, but poor pond maintenance, high stocking
levels and unusual climatic conditions can lead to low dissolved oxygen
(DO) levels. Low DO is likely to occur in summer. As water becomes
warmer it can progressively hold less oxygen: and the fish become more
active, leading to a greater demand for oxygen; and the bacteria in the
pond and filters need more to, as do submerged green plants including
role of submerged plants and algae should perhaps be clarified. During
photosynthesis, submerged plants release oxygen into the water, which
is why they are often called oxygenating plants. However, they also
respire at the same time, extracting oxygen from the water and
excreting carbon dioxide. During daytime they produce more oxygen than
they consume, but at night, when photosynthesis ceases, respiration
continues and they become net oxygen consumers.
if the oxygen demand exceeds the oxygen supply then the DO levels will
gradually decline and this presents a serious danger to the koi. Common
causes of low DO, apart from high fish densities, are heavy feeding and
a dirty pond or filter.
lot of oxygen can be used in oxidizing organic waste and, under certain
conditions, this extra demand may be 'the straw that breaks the camel's
a DO problem often occurs in the early hours of the morning. when we
are not there to see its direct effects on the fish, rather than during
the day when submerged plants are releasing oxygen from photosynthesis.
clinical signs of low DO are lethargy and a tendency for the fish to
gasp at the water surface and congregate around water returns. Many of
these signs are the same as for a gill problem so a test for DO has to
be made to be conclusive. There are cheap DO test-kits available but it
is important to follow the instructions carefully to avoid introducing
oxygen into the water sample by agitation or by pouring water into the
test. If low DO is the problem, i.e. DO is less than 5 to 6 ppm
(mg/litre), then additional aeration will help - but it is essential to
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