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The
latter means is the more satisfactory, especially
if the fishes are to breed in the pond. Also,
the plants greatly benefit the finny population.
Most of the submerged oxygenating plants
have narrow leaves ; these, with the action
of sunlight, absorb the carbonic acid gas
given off by the fishes and other aquatic
animals. This is converted with the aid of
the green colouring matter in the leaves
(i.e., chlorophyll) into nutriment. In the
process, oxygen is formed and is exhaled from
the pores on the underside of the plant's
leaves. In this way oxygen is added to the
water and the poisonous carbonic acid gas
disposed of; at night, however, the process
is reversed, but in lesser degree. Nevertheless,
if there are too many plants in the water,
the fishes may have to face the day with
a " morning after the night before " feeling.
Sagittaria and other plants with their flowers
and, in some cases, part of the foliage out of
the water, provide a fair amount of oxygen ;
also they are ornamental and at the same
time attract insects.
The functions of the marginal plants are
threefold also ; they make the necessary background with their bright leaves and flowers,
their roots and stems provide shelter for small
crustaceans, fish fry, etc., and they harbour
many insects, the grubs of these adding to the
fish's larder. In any case, marginal plants
should be cultivated if only for the natural
look they give the pond.
The next item in the list of pond inhabitants
is his lordship ' the fish,' and here again there
are four types. The first is the predatory and
carnivorous type which, if members of it are
to be kept at all, require separate quarters-
this from their pugnacious and unfriendly
natures. In this category are the Pike, Perch,
Pope and the Sunfishes.
Members of the three following types should
have their place in the pond and all belong
to the great Carp family.
First there are the fishes that swim on the
surface in shoals and are on view always.
They spend their time catching insects and
will leap right out of the water in the enthusiasm of their quest. The Golden Orfe is the
best of this group for the pond, although the
Silver Orfe and the humble Minnow are quite
attractive.
In the next group are the fishes that swim
in mid-water, occasionally visiting the surface ;
Carp, Rudd, Roach, Shubunkins, Hi Goi,
etc. ; they are the backbone, as you might
say, of the fish fauna in the pond.
Finally, there are the bottom fishes that
require less oxygen than the other types.
They live in the deepest part and are seen
rarely, but, although they have no decorative
value, they do inestimable service by acting
as scavengers. Anything that dies and falls
to the bottom, instead of putrifying the water,
is eaten.
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