Oxygen is essential for the well being of all life and that
includes aquatic life. Water adsorbs oxygen from any point where it contacts
air. For this reason a 10ft by 10ft pond having a surface area of 100 square feet
will absorb oxygen from 100 square feet regardless of its depth and so the fish stocking
capacity of a pond is relevant to this calculation. Disturbing the surface with the
use of air stones or turbulent filter returns such as venturis or waterfalls will increase
the surface area because instead of a flat surface the ripples being made produce a wavy
surface. If you can imagine measuring a flat line that measures 10cm long
---------then compare this to measuring a wavy line ~~~~~~ also 10cm long the ups and
downs increase it to maybe double the length. If you try this with a piece of string
you will see what I mean.
Lack of oxygen will cause fish to gasp at the surface
especially in the early morning. Some unexplained fish deaths often at night when
plant life is using up more oxygen than during the day are symptoms of lack of
oxygen. Larger fish which need more oxygen to survive along with fish such as orfe
and rudd (surface swimmers) which are very sensitive to oxygen levels will normally be the
first casualties. Water can also develop an unpleasant smell and appear tainted.
Improving oxygen levels is done by adding features such as
waterfalls, air stones, squirting ornaments and venturis. Reducing the load on your
ponds system is done by ensuring, stocking levels are not too high, adequate filter size
and maintenance, removal of excess algae and blanket weed and reducing the quantity of
plants in the pond.
During warm weather especially humid weather caused by
thunder storms it is vital too maintain adequate aeration. This is because warm
water contains less oxygen than cold water and humid weather also reduces oxygen levels.
