Photosynthesis is the manufacturing of sugars from carbon dioxide and
water, in the presence of chlorophyll and light energy. Oxygen is then
released as waste from the process.
The light source used for photosynthesis is natural daylight. It is
this element of photosynthesis that can be manipulated to stunt the
growth of algae and submerged weeds.
In a pond containing clear water, light easily passes through and any
plants or nutrients present use this to grow. Plants get taller and
grow towards the surface and single cell organisms (such as algae) start
to float towards the surface. It is the floating, or suspended cells
that can make the pond water take on the "pea green soup" look.
By preventing some of the light from reaching below the surface of a
pond, photosynthesis is interrupted in deep-lying pond life such as
algae. However, surface life such as lily pads or reeds, which
photosynthesis either on or above the surface of the water, will not be
affected. As it is not practical or desirable to have ponds built
indoors or permanently covered, it has become necessary to develop
another way of preventing the light from reaching the base of the pond