Pond survey shows tap water bad for ponds

22/06/2009 12:40:17 Don't put tap water in your pond - That's the message from Wildfowl & Wetlands Trust (WWT) this summer as responses start pouring in to their nationwide survey of ponds and backyard wetlands.

June 2009. Initial results from WWT's nationwide survey shows that pond owners' biggest concern is algae which turns ponds green and slimy and can harm wildlife. Algae can spurt into growth when nutrient-rich UK tap water is used to top up ponds. So in the hot dry summer months the best course of action is to wait for the rain and, if possible, prepare for dry spells by collecting as much rainwater as possible.

Top concern is green algae
WWT's Seb Buckton, who has also been advising TV's Kate Humble on her pond [as featured on Springwatch], commented: "The results one month into the survey indicate that summer can bring a wealth of worries for wildlife gardeners. Top of the list of concerns are ponds going green and slimy or covered with a mat of algae - both symptoms of high nutrient levels in ponds - sadly a problem common to wetlands across much of the UK.

Don't top the pond up from your tap
"The practical advice is, if your pond level is getting low, don't panic, it's natural during summer. Topping up a low pond with tap water adds nutrients just at the time it's ripe for an algal bloom. Before you know it you've got a pool of green sludge that takes the oxygen from the water and blocks out the light to the plants below.

Use rainwater or leave alone
"Try collecting as much rainwater as possible - it's as free from pollution as you'll get. Though most people do some rainwater harvesting, many let most of it go down the drain. Not only is this water great for wildlife in your garden, but by diverting it from our drains you could save yourself money on your water bill, and could even help reduce the likelihood of urban flooding during rainstorms."

Fertilizer in your garden boosts algae
In hot, dry weather water evaporates from the surface of ponds and other wetlands. As the water level goes down, nutrients and pollutants are concentrated in the remaining water. Although nutrients help the flowers to grow in your garden and farms to yield big crops, they can trigger unwanted extra-vigorous growth in waterways which stifles the rest of the underwater life.

Tap water in the UK is treated to a high standard so it is safe to drink but often it still contains high levels of nutrients. These nutrients come from fertilizer washed off fields into our waterways, from domestic detergents and from run-off from hard surfaces like roads. Tap water also contains chlorine, added as a disinfectant. Although it looks clear and pure, tap water is not friendly to wildlife in ponds. Adding it when a pond is low can raise nutrient levels and the first things to take hold are often green algae such as blanket weed. A quarter of pond owners so far responding to the survey experiences trouble with this.

Let pond levels drop in summer
The best course of action is to let the water level fluctuate naturally with the weather. Many wetland animals and plants actually like this variation. If you dig a deeper area when you build a pond most aquatic wildlife will have a refuge when the water level drops.

Only 10% using rainwater
If it is necessary to top up a pond, make the most of rainwater to keep it healthy. There are clear financial benefits to rainwater harvesting which are especially visible if you are on a water meter. Yet results show just one in 10 respondents collect all the rainwater from their roofs. Besides wasting all that valuable rainwater, they're missing out on the chance to reduce their water bills with a wastewater abatement (worth £20-40 depending on the water authority). Rainwater harvesting can also save money on metered bills by providing up to 70% of non-drinking water for a household. The less drinking water we use for things like ponds, plants, car washing, and even toilet flushing, the more energy efficient and planet-friendly we will all be.

Pond survey
As part of Wetlands in my backyard, an initiative to maximise the benefit people and wildlife in the UK get from ponds and small wetlands, WWT is running a nationwide survey which runs throughout the summer. The survey will give an insight into how people use water in their gardens, whether for wildlife, for plants, for garden appearance or for sustainability. To fill in the survey visit www.wwt.org.uk/wimby .

WWT supports the Blueprint for Water which sets out 10 steps the government must take to sort out water by 2015. To find out more, click here.

Other top tips for a wonderful wildlife pond in your garden Remove existing blanket weed from the surface of the pond. This takes nutrients out of the system. Use a rake (a leaf rake is ideal) to gently drag the surface layer of algae to the pond edge, and scoop it out. Be careful not to uproot other floating plants. There will be insects and maybe tadpoles caught up in it so its important to leave it on the bank to allow them to wriggle back into the pond. After a few hours, put it on the compost heap (not back into the pond, where it will rot and release the nutrients back into the water).  Allow the pond level to fluctuate naturally as much as possible, and if digging a new pond make a deep area so it will never completely dry out. If you do need to top it up, use rainwater collected in water butts, not tap water. Avoid directing rainwater straight into a pond from your roof, as it will carry sediments that will build up in your pond. Allowing it to collect in a water butt first will let these sediments settle out. It also allows you to use it for other garden jobs like plant watering and even washing the car.

Integer nibh massa Do not keep fish in your pond. These add nutrients to the water in their faeces and some disturb sediments as they feed. They also eat tiny animals (zooplankton) and other grazing animals which normally eat the algae and help keep it under control. Ducks are also a problem on a small pond as they produce significant amounts of faeces, disturb sediments, and may eat submerged oxygenating plants. Don't site your pond close to trees that will drop their leaves in the pond - these are a source of additional nutrients that you could do without. Trees can also shade ponds to the extent that oxygenating plants struggle to survive. Avoid disturbing the sediment in your pond. Nutrients bound to soil particles can dissolve in the water when they are disturbed so don't climb in to clear it out Minimise fertiliser use in the garden, especially in areas ‘upstream' of the pond, to reduce nutrient levels entering the pond in run-off from the rest of your garden.