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PROBLEM SOLVING WITH
OUR POND CLINIC
Help – my pond has turned green!
Green ‘pea-soup’ pond water is caused
by tiny green algae. These, together
with filamentous algae (blanket weed),
and small floating-leaved species, like
duckweed, are boosted by too many
nutrients in the water - especially nitrate
and phosphate.
New ponds or ponds that have recently
been dredged often have temporary
algal blooms. These are usually short-
lived, and the system will settle down
within a season or two, as the number of
tiny zooplankton (water fleas like
Daphnia
)
build up and eat the algae. However,
older ponds which have a persistent
surface cover of duckweed or green-
coloured water are harder to manage.
Controlling algae and duckweed
Controlling algae and floating plants like
duckweed can be difficult - particularly
for larger ponds. The best solution is
to reduce the levels of nutrients in the
water. Other methods are less satisfactory
because they only deal with the
symptoms, so you’ll need to repeat
the treatments.