WHAT'S WRONG ? When a ponds ecosystem becomes
unbalanced a condition known as ‘Green Water is likely to occur, caused by the
growth of a particular type of algae evenly distributed throughout the pond
water. ( Not to be confused with ‘ String Algae’ or ‘Blanket Weed’ which tends
to grow in thick strands or clumps ).
Green water algae are microscopic single
celled organisms that thrive in warm water with high levels of nutrients, and an
abundance of sunlight. For that reason algal problems are prevalent during the
Algae thrive in new ponds where there
are no flourishing plants to provide shade and compete for the available
nutrients, and no natural algal predators to keep the growth of algae under
control. The result is a pond full of water with the appearance of pea soup.
WHAT CAUSES IT ?
Algae control is usually the largest maintenance problem in a pond. When setting
up a new pond it is normal to have excess algae growth until an ecological
balance has been established. This balance is achieved through good water
circulation and the right proportion of floating, marginal, and submerged
plants, fish, and scavengers such as water-snails and tadpoles. Most plants
provide oxygen to the water and all plants absorb nutrients from the water.
Submerged plants (also called oxygenating plants) are beneficial because they
produce especially large quantities of oxygen and provide supplemental food for
fish as well as a place to spawn. Floating plants are most beneficial for
providing shade (important to keep the water cooler as cool water holds more
oxygen and is healthier for your fish), reducing water evaporation, and
providing hiding places for the fish.
Koi ponds are a special case requiring heavy filtration, UVC clarification, and
very high levels of water circulation to maintain the pond in good condition and
combat the growth of algae. Plants and natural scavengers do not survive the
voracious appetite of Koi, consequently Koi ponds must be designed to thrive
without the benefit of these natural elements.
When setting up a new pond it is beneficial to add biological agents such as
CLEARPOND 'Bio-Starter '
Bio Filter Booster
These materials accelerate the growth of the beneficial bacteria known to digest
the organic debris that would otherwise accumulate on the bottom of the pond as
Fish convert oxygen to carbon dioxide and consume insect pests and a little
algae. Scavengers consume algae, decaying plant material and fish waste,
thereby providing nutrients for the plants. Fish excrement, once broken down,
provides nutrients for the plants. It is a complete cycle with each element
depending upon the others to provide what they need to survive.
little algae is natural, will always occur, and is to a certain extent necessary
for a healthy pond. Excessive algae however can be very detrimental to the
ecology of the pond not to mention very unsightly. The quantity of algae in your
pond depends on the weather, the amount of sunlight, the temperature of the
water, the concentration of oxygen in the water and the amount of nutrient and
different kinds of plants present. It can be at its worst in the spring when the
plants are struggling to recover from the winter but water temperatures and
sunlight are on the increase. The situation may clear up once all the plants
have started growing again.
If the pond doesn't clear up on its own, something is out of balance. Algae and
water plants compete for the sunlight and nutrients in your pond. Adding some
extra plants will in time reduce the amount of nutrients available to the algae
and an increase in the amount of surface area covered by water lilies and
floating plants will shade a greater area of pond and decrease the amount of
sunlight available to the algae. This is of particular importance if your pond
is small and shallow. Having too few plants in a sunlit expanse of open water
will result in rapid algal growth due to both the direct action of the sunlight
and its indirect action in heating the water.
As in many complex systems the secret is balance !. So care must be taken to
ensure that excessive vegetation does not cover too much of the surface of the
pond thereby reducing oxygen absorption and causing oxygen depletion of the pond
water. Oxygen is needed in the water to support aquatic life like fish,
tadpoles, and aquatic snails, all of which eat algae and help to keep the ponds
ecosystem in balance.
If you have a good growth of plants and still have too much algae then perhaps
there is an excess of nutrients in the water. This could be caused by a single
factor or a number of different factors in combination.
One such factor could be run-off, check to make sure that garden or lawn
fertilizers are not washing into the pond when it rains. Perhaps you are
over-fertilizing your water lilies or doing it incorrectly. Maybe you have too
many fish, and their excrement is causing a nutrient increase. Maybe you are
overfeeding your fish. These factors must be considered and corrected if
necessary before attempting remedial action to combat the algae itself.
HOW TO FIX IT !.
Having corrected the obvious external sources of contamination affecting your
pond it is time to apply some more direct corrective measures.
It is advisable to start by testing your pond water so that any obvious
deficiencies can be corrected and the effectiveness of subsequent treatments can
be gauged. Look in our section on
Water Treatments & Pond Chemicals
for test kits.
Having tested your pond water, apply the simple corrective measures such as
adjusting acidity (pH) and adding some fresh water to the pond, (no more than
10% at a time) to dilute the nutrient levels. If using tap water be sure to
‘age’ it for several days to remove chlorine before adding it to the pond,
alternatively treat it with a tap water conditioner such as
'INTERPET ‘Fresh Start’
'PondStart' to remove the chlorine and neutralize
other toxic materials.
The second step would be to dose the pond with an appropriate compound from our
range of pond safe products in our Water Treatments & Pond Chemicals
CLEARPOND 'Crystal Lagoon'
INTERPET ‘ Green Away ‘
are suitable treatments specially formulated to be compatible with all aquatic
life including plants. These will cause the algae and spores to clump together
so that they can be easily removed by filtration, or in the absence of
filtration, fall to the bottom of the pond. The use of these treatments to
control algal growth is no more than a short-term solution as algae can develop
resistance and the compounds do not permanently correct the basic imbalance that
leads to uncontrolled growth of algae.
The third step would be to install an appropriate ‘UVC’ clarifier to control
growth of the algae responsible for ‘green pond’. A UVC unit is basically a
tubular chamber inside of which is mounted an ultraviolet lamp. Pond water is
pumped through the unit and exposed to ultraviolet radiation causing the algae
to stick together in ‘clumps’. The clumps of algae are readily removable by
filtration or will fall to the bottom of the pond and form sludge. Excessive
sludge may be removed from your pool with a pond vacuum
cleaner (see our Vacuum cleaner section) and /or treated with a ‘sludge buster’ such as
Interpet ‘ Sludge
See also the OASE
‘Bitron’ and Blagdon Pro
UVC modular range available as stand alone units for out-of-pond applications.
The final and crucial fourth point of attack is biological filtration. Without
adequate filtration it is very difficult to maintain the stable balance of algal
control, water movement and oxygenation, and nutrient levels that guarantee
For the satisfactory control of green water algae the combination of UVC
clarifier and biological filter is essential. See
our filter index. These are biological filtration
systems incorporating UVC units. Reference to the appropriate web page will
enable you to choose the appropriate system for your particular need.
We strongly recommend that before proceeding any further you TEST THE POND WATER WITH A
POND WATER TEST KIT
(*not a pool kit) Unless the pond water is balanced
you could be wasting your money. the best kit is one that conducts at least
5 tests, pH an Kh being the two most critical.
For suitable pond test kits see our selection
Click here for test kits