Curing Greenwater and blanketweed

Green Water and Blanketweed are both different forms of algae, and can cause considerable problems for ponds throughout the year. However, algae control can easily be achieved thanks to Tetra’s range of pond products, designed to maintain a well-balanced environment within your pond.
Green water differs from blanketweed in that it cannot be physically picked out of the pond, whereas blanketweed is stringy and "hair-like" and can be removed manually.

What Causes Green Water?
Green water is caused by the presence of millions of microscopic algae, each of which consists of just one cell. There are many different species of algae that cause green water, for instance Chlamydomonas, Chlorella and Volvox. They occur naturally in almost all bodies of water, and can be a particular problem in ponds during the spring and summer months.
In order to grow, algae requires light and nutrients, an excess of which can result in heavy growth and very green water. In particular, nitrate and phosphate are required, and green water is often accompanied by high levels of these nutrients. Green water is usually worse during the summer months, as the longer days, stronger light levels and warmer temperatures accelerate the rate at which the algae grow and multiply.

What Causes Blanketweed?
Blanketweed is a general term used to describe the many different species of filamentous weed that appear in our ponds.Although there are many different types, some of the most common include Spirogyra, which forms clumps and floating rafts and is slimy to touch, and Cladophora, which has a rough texture and can grow to over a metre in length.
Blanketweed naturally occurs in virtually all bodies of water and is encouraged to grow through the presence of light and nutrients, in particular phosphate and nitrate. Phosphate is a vital component of fish foods and therefore enters the water through uneaten food and fish faeces. Nitrate is produced as the end product of biological filtration and through the natural breakdown of organic matter in the pond.
Nutrient concentrations tend to build up in the pond over time, particularly in the summer when the fish are more active and feeding well.At this time of year, the increased light and warmth, combined with these high nutrient levels, can dramatically accelerate the growth of blanketweed, with some species being capable of doubling their weight in a day or two.

Steps for Avoiding Algae Problems
As well as using TetraPond products, there are also a number of pond management techniques you can use in order to reduce the growth of algae:
Firstly you should only feed your fish on high quality fish foods, such as the TetraPond food range. This is because poor quality diets are not well digested by the fish, resulting in an excess of waste being produced that contributes a greater nutrient load to the pond.This excess of nutrients will then fuel an increased growth of algae. TetraPond foods are highly digestible making them well utilised by the fish, resulting in a minimum of waste. (See the “Feeding Your Pond Fish” leaflet for more information on feeding your fish).
Planting the pond well can also help to limit the growth of algae.This is because many aquatic plants will compete with the algae for nutrients, in particular you should use fast growing species such as Elodea. In addition to reducing the amount of nutrients available to the algae, plants will also shade the pond, depriving it of the light it needs for growth. Floating plants and lilies are ideal for this purpose, and you should aim to cover around a third of the pond surface, taking care not to prevent light from reaching any submerged plants.When potting up plants be sure to use TetraPond Aquatic Compost, as other nonaquatic composts may introduce the wrong balance of nutrients into the pond and encourage algae. (See the “Planting Your Pond” leaflet for more tips on planting).
Keeping the pond clean and refreshed will also help to control algae growth. By performing occasional partial water changes, any nutrients in the pond will be diluted, limiting the algae’s capacity for growth. 25% of the water can be changed every so often, replacing it with tap water that has been conditioned using a dechlorinator such as TetraPond WaterSafe.
Keeping the levels of sediment in the pond low is also a good way of reducing the nutrient load and limiting algae growth.This can be done through the regular use of a pond vacuum, various types of which are available from water gardening outlets. (For more information see the “Keeping a Heathly and Balanced Environment” leaflet).Alternatively, Tetra’s OFX solids handling pumps are designed to pump sediment directly to the filter, without clogging, thereby greatly reducing the amount of sediment left in the pond.

Algae and Your Pond
Both green water and blanketweed can affect the pond environment in a number of different ways, as well as spoiling its overall appearance.

Blanketweed grows rapidly, tangling up pond equipment and smothering plants, whilst green water deprives submerged plants of the light they need to grow. Certain fish species, such as sterlets and sturgeon, cannot cope with blanketweed, becoming tangled in it and suffocating. In addition to this, the general appearance of the pond will be negatively affected by excessive algal growth. Green water prevents you from seeing your fish, and can cause fluctuations in water quality that may harm them.
It is therefore important to control the occurrence of algae in the pond, in order to maintain a correctly balanced environment.

Controlling Green Water
There are three traditional ways of controlling green water:

Ultraviolet lights
The best way of keeping your pond clear of green water is to install an ultraviolet light.These devices are installed before the filter, and work by irradiating the pond water that flows through them with ultraviolet light, killing the algae and allowing it to clump together so that it can be sieved out by the filter.They are an excellent, and permanent, way of keeping the pond free from green water.
It is important to size the ultraviolet light correctly, as their effectiveness depends on the contact time between the light and the water.Therefore, if the water passes through them too quickly they will not work properly. Tetra produce a range of ultraviolet clarifiers, designed to maintain clear water in a range of pond sizes. Each one comes in a clearly labelled box, specifying the pond size and maximum flow rate that it is designed to work at.
The bulb inside the ultraviolet light should be changed approximately once a year, in order to keep the unit working efficiently.The quartz sleeve that protects the bulb should also be checked and cleaned periodically, as if it gets dirty it will cut down the amount of ultraviolet light reaching the water.

TetraPond AlgoRem
If you do not have an ultraviolet light, then green water can be removed through the use of TetraPond AlgoRem.AlgoRem, which is harmless to fish, plants and other aquatic life, clumps the algae together, making it easy to remove from the pond and for the filter to sieve it out. If the clumps are too fine to be removed with a net, then the pond can be left to overflow, the floating clumps running out over the top of the pond. Be sure to use TetraPond WaterSafe if you do this, in order to neutralise the harmful chlorine and heavy metals present in tap water.

“Natural” control
Realistically, it is very difficult to maintain green-free water all year round, without the use of either an ultraviolet light or AlgoRem.The principal of natural control involves the use of aquatic plants in the pond in order to compete with the algae for nutrients and to shade the pond, depriving the algae of essential light.Although it is a good idea to plant the pond well, there will be times of the year when plant growth cannot successfully out-compete the algae that causes green water. (See the “Planting Your Pond” leaflet).

Controlling Blanketweed Growth

TetraPond AlgoFin
There are a number of approaches to controlling blanketweed growth, with some being more successful than others. Tetra has solved this problem with TetraPond AlgoFin, a quick and easy way of killing blanketweed and controlling its spread.Applied as an initial dose to kill the blanketweed, it can then be added at regular intervals to prevent its re-growth. AlgoFin is also harmless to fish, plants and other aquatic life.
A limited amount of natural control is also possible by having a good plant selection.

With the correct pond management, combined with Tetra’s easy-to-use range of pond products, algal problems can be a thing of the past.