1. My pond water has gone green.
If the water is green it is caused by
Green Water algae (or Pea Soup algae)), Green water algae are microscopic
single cell plants that multiply rapidly when conditions are suitable. The
algae will flourish when there are excess plant nutrients in the water e.g.
nitrate and phosphate and excess sunlight to fuel their photosynthesis. As
well as being unsightly this algae can cause potentially lethal changes in
the water pH and oxygen levels. The algae must be controlled and there are
several ways of doing this. For further information –
link to green water
- Increase the stock of pond
plants to out compete the algae for plant food.
plant growth to cover about 2/3rd of the pond surface to reduce
- Pump the water through an
Ultra Violet Clarifier (UV-C)
which kills the algae and clumps it so that it is caught in the filter. Do
not use a UV-C in a new pond for at least 6 – 7 weeks so that the
beneficial bacteria can colonise the filter pads.
- If it is a new pond add
OASE Starter Bacteria to promote the
establishment of beneficial bacteria. It will take up to about seven weeks
for the pond to achieve balance.
- Treat the pond with
Interpet Green Away to kill off the algae
and then regularly dose the pond with
Interpet Extract of Barley Straw.
- Check that there is
sufficient water movement and fit a larger pump and filter if necessary.
The pump should have sufficient capacity to turn over the total volume of
the pond every 2 hours
the algae has been treated dose the pond with
Interpet Sludge Buster to break down the dead algae.
2. The edges of my pond are going green.
Fibrous green strands
of cotton wool like algae called Blanket Weed or String Algae, which if
allowed to grow unchecked, will choke the pond. Blanket weed grows by
utilising excess nutrients in a pond and can rapidly choke plants and
equipment and make the pond look unsightly. Be careful to use blanket weed
treatments that have been especially formulated for garden ponds as these
will have no detrimental effect on the pond eco system. Treatments such as
Interpet Pond Balance and
OASE String Algae Control
are formulated for
pond use and are safe. To control blanket weed the procedures used for green
water algae will also work for blanket weed, with the exception of the UV-C
which has no effect. For further information
Link to Blanket Weed / String Algae
3. Why do I have to run my pump continuously?
The pond water needs to be
circulated continuously to maintain oxygen levels, prevent stagnation and
when used with a filter, remove foreign particles from the water. If you
have an ultra violet clarifier to control green water algae, it must run
24/7 to be effective.
4. Why is a filter necessary?
You have invested time and
money in your garden pond and you expect to be able to see the fish, we have
all heard stories about the green pond in the yard that has been ignored for
a long time that, when finally cleaning it, a number of seemingly healthy
fish are living in it.
For you to be able to see
your fish you need clean water and for clean water you need good circulation
and filtration. Filter are available in three basic types, in pond,
gravity and pressure.
In-pond filters are generally
simple foam blocks or trays fitted to the intake side of the circulation
pump; these are suitable for the smaller pond only.
Gravity filters are
particularly efficient and are generally used for large ponds, particularly
those stocked with Koi; these are large, and very efficient, but the filter boxes cannot be disguised easily as they must be located above the water
level so that the cleaned water can run back into the pond by gravity.
Pressure filters are fitted
inline after the pump and can be buried in the garden up to their lid for
disguise and the outlet can be run up and over a waterfall or creek.
5. How often should I test the pond water?
The water should be tested
weekly so that any subtle changes in water quality can be corrected before
they become a problem.
Test strips by JBL and
OASE are dipped into the water for one second then compared to a supplied
colour chart; from this it is easy to make corrections before they become
have a waterfall on my pond; do I have to run
If you are using the same
pump for the pond circulation as the waterfall you can divert the water so
that the waterfall is run when you want it, but make sure that there is
sufficient thin water (water running over rocks, sprays etc) to provide
It is often better to have a
dedicated waterfall pump which can be operated from a timer so that you can
have the waterfall on when you want it.
7. My pond has a lot of sludge on the bottom, how do I clean it?
The sludge is a mixture of
decaying vegetable matter from the pond plants and algae and is effectively
an underwater compost heap. As this breaks down it releases nutrients into
the pond water which feed the plants and the algae. The sludge can be
removed from the pond with an underwater
8. What is pH?
A measure of water acidity
and alkalinity with neutral being pH 7.0, less than 7 is acid, the lower the
number the more the acidity, over 7 increasingly alkaline. The acceptable
range for a garden pond is between pH 6.5 and 8.5, with the ideal being pH
If the pH falls outside this
range it must be adjusted gradually by dosing the water with
9. How do I work out the correct pump and filter for my pond.
Our web site has a lot of
information on this subject which will help you to correctly size your pump
and filter, see the links on either the pump or filter page and follow the
links, but if you have problems you can always call us for help.
10. How do I find a leak in my pond?
A leak can be very difficult
to locate. First check that all of the plumbing, hoses, fittings, filter,
waterfall or creek etc are intact. If the circulation system does not have
any leaks it must be in the pond.
Mark the water level daily
(or as often as necessary) and when the level does not fall lower, the leak
must be at the water level. Make sure that the level has not fallen too far
so that the fish and pump have sufficient water.
Once the level of the leak
has been established, carefully inspect the liner/pond wall at the water
level to locate the problem. Once the leak has been found it can be repaired
with the appropriate patching system.
11. What is the nitrogen cycle?
Once a pond has matured, a
natural cycle will have developed which, in combination with the pump and
filter, will keep the pond environment in balance. After the first six weeks
beneficial bacteria have colonised the pond, these bacteria are essential as
they convert ammonia from the fish waste to nitrite, then the nitrite to
nitrate which is then used by the plants as fertiliser. For further
information link to
the nitrogen cycle
12. Why is a pump necessary?
A natural pond with no or
minimal wildlife needs a water turnover equal to its volume every two hours
to keep the system healthy. A garden pond is an un-natural size and would
not normally exist in nature so it needs help with a correctly sized pump
and filter to keep the water clean.
13. Why is the carbonate hardness (CH) important?
Carbonate hardness is
the measure of the pond water hardness or softness and is one of the most
important water parameters. The CH level stabilises the pH of the pond water
and prevents any sudden changes in the pH, either up or down, both of which
are equally dangerous. The hardness level must be 4° or greater, levels
lower than this contribute to the formation of ammonia which is toxic to
both fish and plants.
14. Total hardness (TH)
Total hardness is not an
indication of the stability of the pH, this is the function of the carbonate
hardness (CH). The total hardness is the proportion of the magnesium and
calcium ions in the water and is essential for the health of the fish. For
garden ponds the level should be between 8° and 10°.