GREEN WATER

Green water is not bad for Koi, as a matter of fact, it is very good for them and breeders often prefer to keep their water green, because the fish thrive on algae and ensure a good skin quality to the koi and enhance the colours. However, we want to see our fish. Isn't that what Koi keeping is all about??
Very often, the quality of green water is much better than crystal clear water.
The reason why the water turns green is because of the accumulation of nutrients in the water, especially those gathered during winter. The algae blossom on these nutrients, and one must get rid of the nutrients and the algae being the cause and the result.
The other reason for green water (which is linked to the above) is because of the absence of enough bacteria, especially directly after winter, because the bacteria takes a while to grow after the winter months, as it requires enough heat to grow. New ponds always go threw a phase of green water, despite the presence of a UV light. This is nature's way of sorting out a balance. Don't interfere unnecessarily.
There are various options to solve the problem which can and should be used in conjunction with each other, depending on the severity of the problem.

Mechanical way
An affective UV light will clear most of the floating algae which makes your water green. However, it is not effective against blanket weed, the hardy type of algae on the sides and bottom, but these does not affect the colour of the water and can be removed manually if required. One have to remember that the tube is only really effective for a period of one year. So, if you have green water despite the presence of a UV light, a replacement of the tube or an additional light might be an option. It takes a few days to clear the water. When you buy a UV light, always buy a bit bigger than what u actually require. There is not a big difference in the price of a 15-watt and 30-watt UV light. The one is approximately R 550.00 and the other one is R 620.00. We install 30 watt UV lights in ponds of 12 000 litres, although the manufactures indicate that they are good enough for 30 000 litres.
Chemical way
There are various chemicals available on the market, the most common one is "Pond Clear" which is available at most Koi outlets. It is fairly inexpensive at approximately R 75 a jar, which is good for a few treatments on an average pond. This will however cure the situation only temporarily, and it is extremely important to use the right dosages.
Potassium Permanganate can also be used, but it is not advisable for the novice. If you suspect the presence of parasites anyway, this is an option. The Potassium will attack the algae which will make your whole pond brown as it kills the algae within hours, and leave a clean pond a few days later after a water change. However, it also kills beneficial bacteria, unless you can successfully bypass your bio filter.
Plants
Another option is to introduce water plants or more plants that will use all the nutrients and compete with the algae, and the algae will gradually die off. Very often, Koi keepers introduce plants that were planted in nutrient rich soil. This will initially cause the opposite and make your problem worst because it normally causes an algae bloom. Water plants should be planted in normal garden soil with low nutrients mixed with gravel as apposed to compost or rich potting soil.
Bacteria
Most types of bacteria breaks down the nutrients. Introducing a bigger bio filter will cure the pond of algae, but it might take a few months. An option to get the water clear much faster, is to introduce a bale of straw into the water which will generate the right type of bacteria to limit the nutrients in the water. This is why a mature pond normally have crystal clear water, and it is difficult to maintain clear water in a newly build pond younger than 12 months.
Shade
To introduce more shade onto the pond, will also help to clear the green water and it will help to prevent it from happening again to some extent. The higher the temperature, the more algae will grow and the greener the water will be. Your water will always be much clearer in the winter, as the algae does not grow at low temperatures.
Salt
The increase of salt is also an option as it limits the growth of algae. However, it also limits the growth of bacteria and pond plants if the quantity is too much.
Replacement of water
Most people think that the quickest solution is to do more water changes or a total water change, thinking that the clear water added will solve the problem. The opposite happens. New water is rich in nutrients and the algae thrive again. A lot of Koi keepers have leaks in their ponds forcing them to add new water on a regular basis. These koi keepers always battle to keep their water clear.
Patience
In a lot of circumstances, you only need time. Any new pond will go threw a green phase despite the presence of a UV light. Be patient. It will probably clear within a week. Let nature takes it's course. Nature is busy to create a balance. If not, assist nature by doing something about it. Just remember, blanket weed can block your filter and bottom drain and algae can cause bad bacteria and an increase in Nitrites when dying off, which can be detrimental to your Koi.

Hi,

On my existing 3000 litres pond the submersible pump and biofilter is getting blocked with blanket weed almost daily.

What is the quickest way to get rid of it. It is already between 10-15mm long.

The algae that grows on the walls and floor is an essential part of the pond environment. When a pond is mature and this algae has established its self the water will clear.
Never scrub this algae off the walls.
If it is a problem then here is a suggestion - shut the pumps off for about 20 minutes so that the water becomes still. Take some coarse salt and sprinkle the granules onto the long algae. Something like fertilizing a lawn. Leave this to stand for a few hours then turn on the pumps gain.
The salt will kill the algae
In your pond you could quite easily use 3 - 5 kg of salt for this - provided you have not added salt to your pond before.
The salt will be diluted when you give the pond water changes. The secrete is to leave the coarse salt grains sitting in the algae with out circulation.
Regards,
Chris

WARNING!!!

Never ad salt to a pond where formalin or zeolite is present.

If there is a sand filter in your system, it should not be switch off for more then 4 hours.

What is formalin or zeolite?

The active ingredient of Formalin is Formaldehyde, used to preserve dead animals. It is often used to combat protozoal parasites on koi and when mixed with Malachite green, then known as FMC, it is highly effective to cambat White spot and other parasites, even Fluke.

Zeolite is a product added to the pond to eliminate Ammonia.

Alright so I am in the clear there.

The salt will not do anything to the fish right?

Once the blanket weeds dies, I assume it will drop to the floor of the pond and really start clogging up my filters?

You waste will increase for a while yes, and it might increase your Ammonia and Nitrites for a while.

The salt will do nothing to the fish and many hobbyists have salt in their pond on a permanent basis because it has a lot of advantages. It will also combat the negative effect of possible slight Nitrite poisoning due to possible dead organic matter(algae)

Maximum up to 5kg/1000 liters but such high dosage not purely for the combat of algae.

Hi,

I added 4 kg of salt into my 3000 litre pond last week Thursday. The blanket weed is still very much there and looks even longer..

I'm not what to do.

Regards,
Cameron

Any help?

Cam0,

ad another 10kg salt.

I added another 10kg salt. 3 days later all the blanket weed is gone and i'm left with algae on the sides of the pond.

Some interesting calculations I did based on an article on Koi Adventures:

0.1% salt in 1000 Litres is 1.002638522kg
0.3% salt in 1000 Litres is 2.981530343kg
0.6% salt in 1000 Litres is 5.98944591kg
0.15% salt in 1000 Litres is 1.500975634kg

Then it basically went on to say when what %'s should be used.

e.g. 0.15% should be used when nitrites are high in a pond and up to 0.3% is acceptable to prevent parasites in winter. 0.3 - 0.6% to kill parasites and over that (up to 0.9%) for salt baths