Viresco Koi 5g | Blanket Weed Treatment - Water Garden UK

Koi Pond Algae control - 5g treats 12,500L

  • £28.80 inc. VAT

    £24.00 exc. VAT

  • Koi Pond Algae control - 5g treats 12,500L
  • Koi Pond Algae control - 5g treats 12,500L
  • Koi Pond Algae control - 5g treats 12,500L
    • Specifically designed for ponds stocked with Koi Carp, fitted with bottom drains.
    • The formula consists of a 100% strain of the Natural bacterial suppressant for Blanket Weed (String Algae) and Green Water (Single-celled Algae).
    • Treats up to 12,500 litres (2,780 Gallons) of pond water.
    • Viresco treatment will also promote resistance to fish disease and can be used on small ponds or larger lake waters (on request).

    Note: Needs sufficient supply of oxygen to enable effective & prolonged growth of bacteria and to protect fish stock. Please view our Pond & Lake Aerators for suitable oxygenators, if required.

    Find out more
  • QTY

    £28.80 inc. VAT

    £24.00 exc. VAT

  • Pay in 3 interest free payments of £9.60

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  • W. Hockborn
    Took 4 weeks to show an improvement to the water quality but what a difference to the clarity and water quality.
    4 stars

Additional Information

Technical Info

Technical Info

Controlling Algae in Ponds & Lakes.

The presence of algae in ponds and lakes need not necessarily cause a problem. However, in many cases it does and it is advisable to remove it.  Suspended single-celled algae (creating pea green water) can block sunlight from reaching the pond or lake inhabitants and will also absorb vital oxygen from the water body.  

Filamentous Algae (also known as Blanketweed or String Algae) can look very unsightly and may also block pumps and other technology whilst placing stress on the oxygen levels.  If left unchecked, algae will also create a pungent smell.

Single-celled planktonic algae can be controlled in garden ponds by installing an Ultra Violet Filter. The UV light is very effective in agglomerating these single celled algae into clumps that then can be “caught” in the physical filter system attached to the pond.

However, UV filter lights have no effect on filamentous or macrophytic algae and other control methods have to be used.  These methods include the use of chemicals and microbial products.  

Many pond keepers prefer not to use chemical methods.  Our VAqua natural microbial water treatments will reduce and remove the nutrients, notably nitrate and phosphate, on which all algae feed. Planktonic, filamentous and macrophytic algae thus die of starvation.

VAqua natural water treatments will:

  • Clear Ponds and Lakes of problematic blanketweed and algal blooms
  • Digest organic waste on the base of the pond or lake
  • Eliminate nitrate
  • Effectively reduce phosphate levels
  • Improve water clarity
  • Make fish healthier

Water Garden can provide effective biological water treatments for pond and lakes of virtually any size and depth.  Ideally, VAqua treatments should be used together with sufficient water circulation and aeration to aid the breeding process of the bacteria.  Aeration will also help to promote the growth of naturally occuring bacteria.

View Pond Aerators here.

View Lake Aeration Systems here.


What is Algae?

Algae are primitive aquatic plants that differ from other plants in that they have no true stems, leaves or roots. They have a place in the overall food chain as they convert the energy of the sun into forms that can be used as a food source for other aquatic life. Algae also help to increase dissolved oxygen in water. Algae grow in both fresh and salt water systems

There are said to be over 20,000 different named species of green algae.

Algae occur in three different basic forms. These are categorised as planktonic, filamentous and macrophytic.

Planktonic Algae

These are single-celled microscopic plants that float freely in pond water. When planktonic algae are very abundant, they make the water turn green. This is known as an algal “bloom”. More infrequently, the colour of the water can be turned into other colours, e.g. yellow, brown or red.

They include genera of cyanobacteria (the blue green algae, eg Gloeocapsa, Synechococcus, Microcytis) or one of several species of green algae genera (eg Euglena, Scenedesmus, Chlamydomonas).

Filamentous Algae

These algae form as thread-like structures that can be floating or attached to submerged items such as the pond walls or aquatic plants. The description “blanket weed (blanketweed)” is used to describe some of these filamentous algae.

They also include genera of cyanobacteria (eg Nostoc, Anabaena)

Macrophytic Algae

This third category of algae resembles true plants in that they appear to have stems and leaves. They are also attached to the bottom of the pond. The genus Chara is the typical macrophytic algal plant. It occurs in ponds with high levels of calcium carbonate or bicarbonate. Deposits of calcium on the surface of the plants make them feel coarse to the touch. This gives rise to the common name “stonewort”.

Cladophora glomerata (Blanketweed)

The species of filamentous algae that perhaps causes the most concern in fresh water systems around the world is Cladophora glomerata. This is called blanketweed (blanket weed). However, there are over 150 different species of cladophora.

Blanketweed (blanket weed) can grow at tremendous rates when the conditions in the pond are suitable. In very high light levels with high levels of nutrients, blanket weed can grow at over 2 metres per day.

Spirogyra and other Filamentous Algae

Other filamentous algae, also referred to as blanketweed or blanket weed, that cause problems in ponds are species of Spirogyra, Rhizoclonium and Enteromorpha.

Worldwide, there are over 400 different species of the genus Spirogyra. Spirogyra tends to show in ponds as a tangled pond scum. It is also called “water silk”, “silk weed” and “mermaid tresses”. On sunny days, the mats of spirogyra filaments usually float on the surface of the water. They are kept afloat by tiny bubbles of oxygen arising from photosynthesis. These algal mats then sink when the sun goes down and the process reverses as photosynthesis is reduced. As a result, the strands of Spirogyra consume oxygen for cellular respiration. Carbon dioxide is then produced as a waste product. Where there are thick algal mats present, large fluctuations in the dissolved carbon dioxide and oxygen levels in the water can occur. This can lead to rapid changes in the pH of the water that in turn can cause stress and even death to other organisms, eg fish, living in the water.

Enteromorpha intestinalis is another form of blanketweed that occurs in ponds. It is tubular in form and rarely grows longer than about 40cm. There are over 50 different species of the genus Enteromorpha. There are over 20 species of the filamentous genus Rhizoclonium.


Koi Pond Algae control - 5g treats 12,500L

  • £28.80 inc. VAT

    £24.00 exc. VAT

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