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FAQ: Pond Water Problems

By: Dr Gareth Evans - Updated: 29 Apr 2018 | comments*Discuss
Water Ponds Algae Water Quality Hardness

Keeping the water in good condition is an absolutely essential part of maintaining a healthy pond, but sometimes it can seem to be one of those things which is easier said than done!

Fortunately, however, most of the water problems that do occur in garden ponds can usually be fixed, and often, thankfully, without too much of a carry-on.

Here’s our own “top ten” of frequently asked questions about water quality and related issues.

It’s surprising how often the same concerns and queries keep cropping up, so if you have a problem in your pond, there’s a good chance you should find the answer to it amongst them.

1. Why’s My Pond Water Gone Green?

The simple answer is that it’s full of unicellular algae. It tends to be a problem for newly constructed ponds, but older ones can also suffer, especially in the spring as the days lengthen and the sun begins to shine more.

It’s principally due to an excess of nutrients – chiefly nitrates – in the water, which give these single-celled plants a head start and allow them to grow and multiply quickly. Cutting back on the amount of dead plant material in the pond, clearing out any fallen leaves and not over-feeding the fish often makes all the difference.

2. What Is Water Maturation?

Before you plant any new pond – and long before you think about introducing any fish – the water needs to mature. It simply means allowing it to settle and turn from being tap-water full of chlorine and chemicals into a more natural pond water. The process is also sometimes known as “conditioning”.

3. What Is Hard/Soft Water?

Whether water is considered “hard” or “soft” depends on the levels of dissolved calcium it contains – the more calcium, the harder the water. Rainwater naturally contains none, but it picks it up as it flows over rock and through soil so the geology of your local area influences the softness or hardness of the water supplied.

As a rough guide, the water in Scotland, most of Wales and Cornwall tends to be soft, while in the Midlands it is hard and very hard throughout most of the rest of England – though individual areas do vary. It can be important for the pond keeper because some plants and pond animals have particular needs and also because it can sometimes also affect aspects of the water chemistry too.

4. What Is pH And Why Is It Important?

It is the measure of the acidity or alkalinity of the water – and strictly speaking it relates to the hydrogen ions present. A pH of about 7 is “neutral”; the higher the number the more alkaline the water and the lower the pH, the more acidic it is.

Most pond-life prefers water around neutral, although some favour slightly acidic or slightly alkaline conditions; again pH can affect water chemistry, so it’s an important factor in overall water quality.

5. How Can I Control Blanket Weed Algae?

Options for controlling blanket weed include dosing with barley straw – an old traditional and surprisingly effective method, algaecides, nutrient removers and a range of electronic devices which use electrical discharges or ultrasonic waves to break up the algal strands.

6. Why Are My Fish Gasping For Air In The Summer?

Warm water naturally holds less oxygen than cold, so the rise in temperature at a time when the fish are active and feeding the most will tend to expose any problems in water aeration. Poor oxygenation can be caused by a broken or blocked pump, the sudden onset of the dreaded “green water”, the arrival of excess nutrients in the water, evaporation or simply too many fish. The only cure is to determine the underlying cause and deal with it – quickly!.

7. What Are The Key Factors For Water Quality?

The key factors are: pH, dissolved oxygen, ammonia, nitrite, nitrate, carbonate and calcium levels (hardness).

8. How Can I Stay On Top Of Water Quality?

The only way is by routine testing. A good testing regime can often allow you to spot problems as they develop and deal with them long before they become a serious threat to the well-being of your pond. Regular testing is essential for new ponds, but even for established ones, fortnightly testing will help you keep an eye on what’s going on.

9. Why Are Leaves/Grass Clippings Such A Problem?

Too much plant material in the pond fuels bacterial growth as the microbes break down the leaves or grass. All this activity by these bugs uses up a great deal of the water’s dissolved oxygen while also adding excess nutrients to the pond, which in turn encourages algae.

10. Can I Get A Water Treatment For.............?

Water treatments are very big business and a huge range are available to deal with most of the common pond ills. As well as barley straw and algaecides there are buffers to regulate pH, de-chlorinators to remove the chlorine from tap-water, anti-foaming agents, “sludge busting” treatments, specialist pond fertilisers and a whole variety of medications for fish disease.

Water quality is, obviously, vital for the aquatic environment – especially if the pond contains fish; according to some estimates, it can account for as much as 90 per cent of all their health and husbandry problems. It really is small wonder that so many of us are preoccupied with ensuring that our own pond-water stays in good order.

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Share Your Story, Join the Discussion or Seek Advice..
Within the last 3-4 weeks my pond has significantly taken a turn for the worse. It has developed a very thin film on top (although not oily to the touch), & pinky purple stringy droplets have started forming on the oxygenating plants (which look like they have started to die - disintegrating to the touch) & on the liner of the pond (& getting worse by the day). It is a good sized garden pond (about 6 metres by 2 metres) & still has good wildlife (tadpoles, newts, dragonfly nymphs & pond snails all seem to be thriving), but I am very worried that things will slowly start to die off. I have seen dogs & sheep both go in my pond & wonder if anything has transferred off their coats? I have ordered a pond testing kit to check pH etc, but would be extremely grateful for any advice. Many thanks
Crazy Ferret Woman - 29-Apr-18 @ 7:50 PM
@Perere. Sorry, we try to avoid mentioning specific product names if we can. There are many good PH meters out there, try looking for those that have been reviewed and given 5 stars.
PondExpert - 7-Jan-15 @ 11:15 AM
What is the best PH Pond Water Meter or Reader to buy pls.
Perere - 4-Jan-15 @ 2:12 PM
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