Irrigation & Water  


Managing Garden Ponds

Typical Problems associated with garden ponds

Algal growth – filamentous algae (blanket weed)
Unicellular algae (green water). Heavy algal growth is caused by an excess of dissolved nutrients in the water which can originate from a nutrient rich water source or excessive organic silt in the pond.

Cloudy Water in addition to unicellular algae this can also be caused by fine suspended solids originating from fish excreta and disturbed bottom sediment.

Foul odours  a deeper accumulation of silt can quickly turn anaerobic (lose all of its oxygen) particularly in warmer weather. Microbes that thrive in these anaerobic conditions can release noxious smelling gases – such as hydrogen sulphide which has the characteristic odour of rotten eggs as part of their metabolism.

Symbio Blue Water has been designed to prevent all these common problems and can be used as a maintenance product  for all garden ponds

How Blue Water Works

Symbio Blue Water contains large numbers of a variety of strains of naturally occurring harmless bacteria which ahas been designed to perform the following functions:

Preventing Heavy Algal Growth - Reduction of dissolved nutrients. The bacteria in blue water have the use the dissolved nutrients that fuel algal growth as a food source reducing the potential for algal growth.

Reducing Water Cloudiness and Silt Levels - The bacteria in blue water are able to degrade the organic solids that cause an increase in silt levels and can also become suspended in the water column reducing water clarity.

Improving Water Quality For Pond Life - The accumulation of organic matter in a pond -particularly if there are fish - can result in the build up of toxic compounds (ammonia and nitrites) in the water. These compounds are stressful to the fish and other pond life and can make them more susceptible to disease. The bacteria in the blue water are able to degrade these toxic compounds improving water quality and making the pond a healthier environment for fish, amphibians and other aquatic animal life.

Dosage Rate & Application

Fizzy Tab Application Rate: 

Less than 500 litres (110 gallons) 2-4 tablets per month.
500 – 5000 litres (110-1,100 gallons) 4-8 tablets per month.
Up to 50,000 litres (11,000 gallons) 8-20 tablets

For ponds of more than 50,000 litres contact Symbio for advice on the most appropriate management options.

Blue Water Junior Application Rate:

 For ponds less than 22m3 (5,000 gallons) place 1 Symbio Blue Water Junior sachet in the pond per 11m3 (2500 gallons) every month during the summer.

For ponds greater than this place 1 sachet in the pond per 22m3 every 2 weeks over the summer

If  blanket weed growth is heavy, as much weed as possible should be removed before treatment. Any blanket weed should be left at the side of the pond for a day to allow any trapped pond life to escape back to the pond.


How to Calculate Water Volume

Measuring Water Volume

Water volume is measured by multiplying the surface area of the pond by its depth. If all measurements are made in metres your result will be in m3

Example: A rectangular pond with sides 2m and 4m in length and with a depth of 60cm will have a volume of: 2m x 4m x 0.6m = 4.8m3

A round pond is more difficult to calculate but can be measured in the following way:  Measure the distance from the middle to the edge of the
pond (the radius), square this result and then multiply by 3.14. Then multiply this result by the depth.

Example: A round pond with a radius of 2.5 metres and a depth of 60cm will have a volume of: 2.5 x 2.5 = 6.25 6.25 x 3.14 = 19.63 19.63 x 0.6 = 11.8m3

Additional Ways to Improve your Pond

The regular use of  Symbio Blue Water will make many improvements to your pond but you will maximise the health and appearance of a pond using the following tips.

Water Sources

The quality of the water used to fill and maintain levels in the pond can have a dramatic effect on how easy a pond is to manage.

Mains water typically has high levels of dissolved nutrients which can cause rapid and heavy algal growth. As such this should be used sparingly as a water source and where possible replaced by stored rainwater or surface run off.

If a pond is fed by surface drainage from lands that is fertilised, or a stream source that is subject to nutrient run off, heavy algal growth will also result.


A healthy population of various aquatic plants will also help to improve the health of a pond. Generally, growing plants help to remove the nutrients from the water that stimulate algal growth and they can also provide a habitat and food source for other pond life. The most appropriate planting will depend on the type size and depth of your pond and you should satisfy yourself that you are introducing the most appropriate plant into your pond as rectifying mistakes can be time consuming and costly.

Surface Cover

An important aspect of any planting scheme is to provide some surface cover to the pond which is achieved by introducing floating plants such as lilies. This has the combined benefits of shading the pond from sunlight and reducing the potential for algal growth and to provide a shelter for any fish during hot weather.

Leaf Fall and Windblown debris
It is important to prevent the accumulation of fallen laves in your pond. This can be done by either putting a net over the pond in autumn to catch the leaves, to regularly remove any floating leaves form the pond with a net or to carefully remove sunken leaves with a net or rake being careful not to cause too much disturbance to the pond in the process.

Oxygenation & Water Movement
As well as providing an attractive addition to a pond fountains and water falls have the additional benefit of providing oxygen to the water to create a more healthy environment for fish and the movement of water can also help to prevent the growth of blanket weed and other green algae that preferable grows in still water.

Adding gravel of pea shingle to a pond provides a medium with a large surface area that encourages the colonisation with beneficial bacteria. This helps to reduce the build up of toxic compounds and nutrients in the water creating a more healthy environment for fish and helping to reduce algal growth.


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