Suspended algae turn pond water green
The last time you checked, your pond water was nice and clear; now, just a few days later, it has been turned green by suspended algae. Discover why you often find green water in contaminated and freshly created ponds and what you can do about it.
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Green pond water: newly created ponds

Pond water is never completely clear. However, when it becomes so discoloured and green-soup-like that visibility is restricted to no more than a few centimetres, you most likely have an algae plague.

In the case of newly created ponds, it is far from unusual for the water to temporarily turn green. In the early days when the ecosystem is not yet fully established and properly aligned, suspended algae can quickly take over.

But why do suspended algae turn pond water green? Most microscopic algae photosynthesise. To do this, they contain green chlorophyll, which ultimately turns the pond water green.

Suspended algae turn pond water green: assistance from animals

Natural algae eaters like copepods and daphnia eat suspended algae. These little creatures can therefore help to destroy algae – but that is all they will do. As a matter of interest, small crustaceans are not only algae eaters and a good form of natural food for fish, but also a sign of a good pond ecosystem.

Despite the above, copepods and daphnia are not the only creatures that can help combat suspended algae; silver carp and pond mussels are also sometimes recommended and used for this purpose. However, you should not expect miracles. Furthermore, you also risk creating other problems for yourself as silver carp can grow to about a metre in size, making them far too large for most garden ponds.

Suspended algae turn pond water green: too many nutrients

Too many fish, excessive feeding, low-quality food or a lack of pond hygiene and mismanagement can lead to a garden pond containing too many nutrients and favouring algae growth. If, as is often the case in colder temperatures, a pond has too few underwater and pond-side plants, which would otherwise make use of these nutrients, ideal conditions for an algae plague are created. The phrase ‘competition for nutrients’ is commonly used in this regard.

The best ways to prevent suspended algae include controlling your fish stock and the amount of food you administer as well as using high-quality food. It is also important to observe the basic principles of good pond care. In the long term, you will then no longer face the issue of suspended algae suddenly turning your pond water green.

Combating green pond water with a UV filter

In the event of a plague of suspended algae, a UV clarifier (also commonly known as a UV filter) can prove extremely useful. This is usually installed upstream of the pond filter system but it is important to note that only the suspended algae that is sucked in by the pond pump and fed through the UV clarifier will be destroyed. Its position in the pond is therefore decisive. Furthermore, the clarifier should not be used on a permanent basis.

Preventing suspended algae

To sustainably avoid algae plagues like green pond water, it is important to ensure good water quality, conduct partial water changes and remove sediment in a timely manner as well as to keep your fish stock and feeding activities under control. For more about pond care, simply click here.

Product recommendation:

Tetra Pond AlgoRem*

24-hour immediate relief against floating algae (green water).

Tetra Pond AlgoFin*

Reliably and effectively destroys stubborn blanketweed and other species of algae in garden ponds.

Tetra Pond Test 6in1

Test strips to quickly and easily check six water quality parameters in 60 seconds

AUTHOR: Tetra GmbH
DATE: 30.01.2017