There are few things more disappointing for the water gardener than to see the water of your lovingly built pond turn soupy green. In the past, dealing with the curse of green water could often turn into a major headache, but today, combining some of the old, time-honoured remedies with a spot of modern technology can usually be relied on to sort the problem out, once and for all.
What is green pond water caused by?
Green water is caused by the growth of large numbers of single-celled algae, which live suspended in the water and is fuelled by light and excess nutrients in the water – typically making its appearance as the days begin to get sunnier in the spring.
Although it is most commonly encountered in recently constructed ponds, where the water chemistry and planting has not yet settled down, older, more established water features are not immune.
The principal culprit is nitrate, a nutrient which forms naturally as left-over fish food, fish faeces and dead plant material decays. Nitrate test kits are widely available and very simple to use, but often simply clearing out fallen leaves, cutting and discarding dead water-plant foliage and avoiding over-feeding your fish can make a big difference.
Natural control methods for green pond water
A variety of methods can help to deal with green water. Natural methods include avoiding fertilising the pond itself – nor the area around it – removing decaying matter, not over-stocking with fish and sensible planting.
Surface plants compete with algae for light and so having as much as a half or two-thirds of your pond covered with vegetation can make a big difference, while trees or bushes can also be used to give shade, further helping to reduce the levels of sunlight reaching the water. However, these approaches may not always be enough in themselves, as green water may still happen in early spring, before the protective plants have developed new foliage.
For another natural additive, barley straw could fit the bill. Administered either as pouches of straw, or doses of straw extract, it is an approach which some have hailed as a miracle cure – though not all pond-keepers are unanimous in this opinion. It takes a month or two to show any effect, but the natural enzymes are said to have remarkable abilities to inhibit algal growth – making it effective against blanket weed also.
Chemical treatments for green pond water
Chemical treatments are also available to deal with the problem. Although they can be expensive and do not provide lasting protection, they can be very effective, particularly for newly constructed ponds. They must be chosen carefully if the pond has already been planted or stocked with fish and if you do decide to go down this route, then reading the label carefully and using the product in accordance with the instruction is obviously critical.
Perhaps the single greatest advance in recent years in the battle against green water has been the development of reliable and affordable ultra-violet (UV) clarifiers. Aside of its effectiveness in destroying the algae which cause the problem, this approach has a number of other advantages. It has no effect on water quality and because it takes place away from the pond itself, it poses no threat to the plants or fish. Easy to install and cheap to run, a good quality UV unit combined with a biological filter system and an appropriate planting regime offers the best possible means of dealing with the green water scourge – though it is important to remember to change the UV bulbs every year. A number of manufacturers produce UV units to suit a range of pond sizes, widely available from garden centres and other retail outlets.
Left unchecked, green water algae can turn the most beautiful of water features into a pitiful sight in a very short time, but the good news is that with a little careful thought and a bit of practical effort, it should be fairly straightforward to keep your pond crystal clear.
A primer for Pond Water, and why it is important.
Pond water serves as a habitat not just to fish but many microorganisms that we can’t even see with our naked eye, yet they play an important role in keeping the water quality at its best. The quality of water is judged by several parameters which help in understanding how contaminated it is for aquatic life. These parameters include the oxygen level, carbon dioxide level, salinity and temperature of the pond water.
One might question why it is important to measure these parameters, a pond is an ecosystem which will only survive when these factors are at an optimum level for the aquatic life to survive in, which includes plants around a pond as well.
How do I measure the quality of the pond water?
Out of all these parameters, the level of dissolved oxygen is the most crucial as the feeding patterns and immunity of fishes depend on it. A dissolved oxygen meter (DO meter) is used to measure the levels of oxygen, normal level being 4 ppm (parts per million). Low oxygen levels occur if there are algal blooms crashing in the pond water, this happens due to the consumption of high oxygen levels during the decomposition of algae.
Low oxygenated pond water and dangerous gasses
When levels of oxygen are dangerously low, levels of harmful gasses such as carbon dioxide increase. CO2 makes it difficult for the fish to take oxygen, causing death. Temperature is another important parameter which affects feeding of the aquatic animals, and the levels of oxygen consumption in water. Although fish change their temperature according to the external temperature in order to survive, they cannot tolerate abrupt temperature changes. These sudden changes occur when fishes are put into a pond from an aquarium without letting them first adapt progressively to the temperature. To regulate the temperature, aerators are used which can help in controlling the pond water temperature when transferring the fishes. These parameters are linked to each other which is helpful and makes the process easier to understand for people who are new at maintaining a pond.
Detecting problems from green pond water
Regularly checking the parameters will allow you to understand how all these parameters are related along with the feeding patterns of fishes. Growth and health of these fish will be easier to monitor, along with the health of the plants nearby the pond. More than one parameter is mentioned since a single parameter might not help you see the whole picture but the way these variables interact help to judge the quality of pond water. The sooner you detect the problem, treatment with oxygen pumps, aerators and even aquatic plants could be used to minimise the damage and bring the parameters back to normal.