How Viresco Aqua algae control works

Viresco Aqua works as an algae control product by removing nitrate from pond water. It is only when the nitrate has been taken down to zero that the algae dies from starvation. The time taken to reduce nitrate to zero varies considerably. For some people it takes a few days; for others it can be several weeks.

The rate at which the nitrate falls depends on a whole host of different aspects. These include water temperature, (the colder the water, the longer it takes), fish stocking levels, feeding regime (i.e. frequency of feeding and quantity and type of food used), topping up the pond with nitrate-containing tapwater, topping up with rainwater that can contain significant amounts of nitrate, water run-off from surrounding land, streams that may enter the pond etc.

Whilst some people realise that some tapwater can contain relatively high amounts of nitrate, many people do not appreciate that relatively high levels of nitrate can arise in rainwater, particularly if the pond is in an urban area or near a motorway. This is because vehicle exhaust gases contain nitrogen peroxide and, when it rains, this falls as dilute nitric acid.

If there is still some nitrate in the water (be it 50 parts per million or 5 parts per million), there remains enough food for the blanketweed or algae bloom and it will continue to grow.

We advise that the nitrate level should be checked before Viresco Aqua is put into the pond water and then again after, say, after 7 to 10 days. If the pondkeeper does these nitrate checks, he will see how our product is working. The nitrate has to drop to zero before the algae - blanketweed or greenwater - dies of starvation. For some people, the product works quickly, i.e. within a few days, but for most people it takes considerably longer.

Some pondkeepers claim, correctly, their blanketweed seems to be growing faster after Viresco Aqua has been applied. This can be very much the case at certain times of the year. The reason for this increase in growth rate is that the number of hours of sunlight in a day is increasing in Spring and early Summer. As we move into Summer the strength of the sunlight also increases and the water becomes warmer. All these changes cause blanketweed to grow even faster.

Remember, blanketweed and algae bloom can grow if there are very small amounts of food (nitrate) in the water, so it will continue to grow until Viresco Aqua has brought the levels to zero.

What are the benefits of using Viresco Aqua in ponds?

Viresco Aqua will give three basic benefits to the pond keeper. It will reduce and remove nutrients (nitrate and phosphate) in the pond water that feed algae. As a result, blanketweed (string algae) and algae bloom (green water) die of starvation. Secondly, Viresco Aqua will digest waste organic matter in the pond. Thirdly, Viresco Aqua will improve the health, growth and disease resistance of fish.

What is in Viresco Aqua?

Viresco Aqua is a mix of two groups of micro-organism based items. One group removes the nutrients - notably nitrate and phosphate - from pond water and the other group digests organic waste on the bottoms and sides of ponds.

How is Viresco Aqua applied?

Viresco Aqua is a dry powder. We advise that the appropriate amount be mixed into half a bucket to a bucketful of water and allowed to stand for a few hours. The water should be taken from the pond. Ideally it should be mixed in the morning and applied to the pond in the evening. Also some air should be introduced into the solution via the use of an air stone or regular whisking. Never leave the solution for more than 24 hours before applying to the pond.

Should Viresco Aqua be put into the pond or into the filter?

Most people put the solution of Viresco Aqua directly into the pond although some put the concentrated solution directly into the filter.

How frequently should Viresco Aqua be used and how long does it last in the pond?

Some of our customers make one application and then see no more blanketweed for over one full year. Others keep blanketweed at bay for a few months with one application. However, a minority of pondkeepers need more than one dose to suppress blanketweed. Remember, every pond is different.

Should the pondkeeper apply maintenance doses of Viresco Aqua?

It makes sense to consider the application of maintenance doses. However, unlike recommendations for some other products, we do not suggest what and when these should be. We advise that nitrate levels should be regularly checked and the readings used as a guide as to when more Viresco Aqua should be added.

What difference do fish stocking levels and overfeeding make?

Many ponds have filters with capacities that are far greater than those needed for the ponds' volume. More fish tend to be introduced knowing that the filters can cope with the increased amounts of ammonia. Where this is the case, then more Viresco Aqua than our suggested dose should be used. The amount required is linked to the increased amounts of ammonia produced rather than just straight water volume. As a guideline, if there are more than 2.5kg of fish weight per 1000 gallons of water, then more Viresco Aqua should be used.

Similarly, where overfeeding occurs or when very high protein foods are used, more ammonia is produced. More ammonia means more nitrite and more nitrate. More Viresco Aqua should then be used.

How quickly does Viresco Aqua work?

Many people see blanketweed dying back within 4 to 5 days. For others it does take longer. For most people it occurs within about 3-4 weeks. If, after this time, no noticeable change has taken place, then apply a second dose.

What happens as the Viresco Aqua starts to work?

The colour of the blanketweed starts to change from green towards brown. It also becomes brittle and pieces break off. Some people have reported that pH levels in the pondwater increase as the blanketweed dies.

Should the blanketweed be removed before applying Viresco Aqua?

We would advise that as much of the blanketweed as possible should be wound out before the Viresco Aqua is applied. This will reduce the need to clean up weed debris after it has died. It will also keep better control over rising pH levels.

Is Viresco Aqua safe for fish?

Yes, Viresco Aqua is safe for fish. It was initially formulated for use in commercial fish farming to improve the growth, health and disease resistance of the fish. The fact that it suppressed algae growth by removing the nutrients on which algae feed turned out to be a bonus.

What effect has Viresco Aqua on the health of fish?

Viresco Aqua improves the health of fish. They eat better and grow quicker. They are less prone to fungal and bacterial diseases. Many of our customers have referred to their fish becoming "more lively". One customer first bought the product at the end of May 2001. Exactly seven days later, she rang to say that the nitrate in the pond was zero and the blanketweed was gone. Her object was to take the nitrate to zero as she knew her koi would be healthier. She admitted her fish were now "different creatures".

How does Viresco Aqua improve the health and disease resistance of the fish?

The reason why a fish succumbs to a bacterial or fungal disease is the bacteria or fungi that form the disease have become predominant. If the pond system were kept in better balance and the disease microbes had greater competition, then they would not become predominant and form the disease. The micro-organisms in Viresco Aqua are present in huge numbers and in a number of different species. They do not remove the disease forming species but compete with them for food and space and keep their numbers down so they do not take over.

Is Viresco Aqua safe for other wildlife?

Yes, there is no problem for other wildlife, e.g. wild birds, fish, frogs, newts, pets, plants, insects and humans.

Does Viresco Aqua harm plants?

No, Viresco Aqua does no harm to plants. However, because Viresco Aqua reduces nitrate levels in the water, plants may grow less strongly. For example, leaves of, say, water lilies grow less vigorously but the bonus is that they should flower better.

Are the Viresco Aqua products chemicals?

All Viresco Aqua products are micro-organism based and the method of operation is biological and not chemical. Viresco Aqua contains a number of species of micro-organism carried on bran. In addition there are support nutrients which are included in the mixes.

What about the use of salt in koi ponds?

There is some evidence that using salt can inhibit the effect of Viresco Aqua. We have had reported by one customer that salt levels of over half an ounce per gallon can affect Viresco Aqua.

What about magnets?

Magnetic blanketweed control products do not affect the microbes in Viresco Aqua.

Can I use Viresco Aqua with chemicals?

Any fungicidal chemical that knocks back the microbes in a filter system will also knock back the microbes in our Viresco Aqua products. Wait until these chemicals have dissipated. An example of such a chemical is potassium permanganate

However, other chemicals that are known not to affect microbes can be used at the same time as Viresco Aqua. Many people use branded herbicides to remove blanketweed and these types of products would not normally lower the efficacy of Viresco Aqua. However, it still would be best to leave a gap of a few days between using any injurious chemical and using Viresco Aqua.

How do water changes affect the efficacy of Viresco Aqua?

Obviously as water is removed from a pond, the microbes in that water will be lost. However, because micro-organisms are always growing and multiplying as long as there is food and space available, those that remain in the pond will increase in numbers until a microbial balance is reached.

What does Viresco Aqua do to the micro-organisms in the filter?

Viresco Aqua helps to maintain an efficient biological filter as it contains microbes that are used in the nitrifying process in the filter.

Is Viresco Aqua temperature dependent?

Yes, Viresco Aqua works best in water temperatures above about 10°C (50°F). However, it will work in lower temperatures but more sluggishly.

Can Viresco Aqua be over-dosed?

Yes, Viresco Aqua can be over-dosed with no problem. It is organic, not chemical. We have one customer who each year uses 6 times our recommended dose all at once and for over four years has not seen any blanketweed. The only qualification is that enough oxygen should be present in the pond when Viresco Aqua is used. So, ensure that you have a filter, oxygenating plants, waterfall, fountain or an airstone. The waste-digesting microbes in Viresco Aqua will take oxygen from the water, which fish need, so it is important that there is plenty of oxygen available.

What effect does Viresco Aqua have on nitrate and phosphate?

Viresco Aqua removes the nitrate arising from the biological filter. Nitrate is formed from the conversion of nitrite that in turn has been oxidised from ammonia. Nitrate can be reduced to zero within a few days and kept at zero by the action of the microbes in Viresco Aqua. Phosphate is also reduced but usually much more slowly. When the nitrate level in the pondwater is zero or very, very low there is no food available for the algae - either blanketweed or algae bloom.

Do pH levels affect Viresco Aqua?

We are finding that, in high pH water, Viresco Aqua seems to take longer to work.

What is the effect of UV light and UV filters on Viresco Aqua?

It is widely accepted that ultra violet light from the sky does destroy bacteria. In order to protect the bacteria in Viresco Aqua, we recommend that the solution of the product be applied to the pond in the evening, during low daylight levels followed by a period of darkness. Initially, we also recommended that UV filters be turned off as the UV light from them could affect the efficacy of the product. However, we now believe that UV filters can be left on as the intensity of the emitted light is generally not enough to kill bacteria.

UV lights are primarily used to agglomerate algae bloom, the clumps of which are caught up in the physical filter. Viresco Aqua removes the nutrients on which both blanketweed and algae bloom live, so there should be no need to use a UV filter once the nitrate levels have been taken to zero.

It is still advisable to apply the product to the pond in the evening as the intensity of UV from daylight, even on bright cloudy is considerably greater than the UV from pond filters.

What is the shelf life of Viresco Aqua?

The Viresco Aqua microbial products are purposely put out as soluble powders. There is a tendency for the powder to solidify over time. There is no problem with this. The Viresco Aqua range, unlike microbial products in liquid form, have unlimited shelf lives if kept dry. Liquid microbial products deteriorate over time. The end user of a liquid product is usually uncertain of its shelf life.

How long has Viresco Aqua been on the market?

Viresco Aqua was launched as a blanketweed control product in autumn 1997.

Is Viresco Aqua safe to use around animals, pets or humans?

Yes. Viresco Aqua is entirely safe for humans - it is not a chemical or a pesticide and is non-toxic. Please follow the instructions on the pack, and ensure to wash your hands after use. If spilled or sprayed onto the skin or eye area, rinse immediately with cold water. Not for human consumption, so please store safely.

How much Viresco do I need for my pond?

To help you work out how much Viresco you'll need to treat any given pond size, our site now features a Viresco pond capacity calculator:

How much do I need?

Our pack sizes

• 2.5g Small Pond Pack treats 6,500 litres (1,429 gallons)
• 5g Medium Pond Pack treats 12,500 litres (2,749 gallons)
• 10g Large Pond Pack treats 25,000 litres (5,499 gallons)
• 25g Extra Large Pond Pack treats 70,000 litres (15,398 gallons)