Spring Pond Maintenance Tasks for Healthier Water

Why Spring Work Matters More Than Any Other Season

By early March, your pond is already busy. Frogs and toads are heading back, newts are stirring in the silt, and the first insects are hatching in the shallows. Water, though, lags a long way behind the air. A mild afternoon in the garden means very little to creatures sitting in six degrees of water, which is why spring maintenance needs to be done thoughtfully rather than energetically.

What you do over the next few weeks shapes the entire year. Clear the winter's debris, thin out crowded plants and get filtration running before the water warms, and you will spend the summer enjoying your pond rather than fighting green water. The ideal window in most of the UK is late February to mid-April, and it is worth finishing the heaviest jobs before frogspawn appears in earnest.

Clear Debris While the Pond Is Still Quiet

Fallen leaves, twigs and the last of the blanketweed all break down in the water, releasing nutrients that feed algae later on. Remove them now with a soft rake or a long-handled net, working from the edges inwards. Take out no more than a third of the accumulated silt in any one year, as the rest is home to invertebrates, and never be tempted to empty and scrub the pond clean.

Whatever you pull out, leave it on the pond edge for a day. Small creatures — water beetles, damselfly larvae, the odd newt — will crawl back to the water on their own.

• Skim floating debris with a net rather than a rake where spawn may be present.
• Trim dead foliage from marginals, but stop cutting at the waterline.
• Avoid wading in; kneel on a plank to spread your weight and protect the liner.
• Check the pump intake is not clogged with leaves before you switch anything on.

If you use a net over the pond in autumn, this is the moment to take it off. Leave it any longer and you risk trapping amphibians and hedgehogs as they move about at night.

Divide and Reinvigorate Overgrown Plants

Marginals and oxygenators spread quickly, and by their third spring many are root-bound and pushing the water's edge out of shape. Lift them gently with a fork, split the rootball with two forks back to back, and replant the healthiest sections in aquatic baskets using a low-nutrient aquatic compost topped with gravel. Reject anything with a hint of phosphate-rich general-purpose compost, which will simply feed the algae.

Water lilies benefit from the same treatment every few years; divide the rhizome so each piece has a growing point, and repot into a larger basket set at the same depth as before. Thin oxygenating plants such as hornwort and water starwort by roughly a third, keeping the freshest growth. Native species suit British ponds best — marsh marigold, water forget-me-not and flowering rush all earn their place, feeding insects as well as looking well.

Check Pumps, Filters and Pipework

Bring the pump out of the water and inspect it before it goes back in. Grit and plant fragments collect around the impeller over winter and are a common cause of early-season failure. Clean the housing, check the impeller spins freely by hand, and examine the cable and any joints for cracks. Replace UV bulbs every six to twelve months, ideally at the start of the season when the lamp is doing the most work.

Filter media should be rinsed only in a bucket of pond water. Tap water will kill the bacteria that convert fish waste into less harmful forms, and a filter that has lost its colony is little better than a box of gravel. Once everything is running, top the pond up with rainwater from a butt where you can; if tap water is unavoidable, use a suitable dechlorinator and add it slowly.

Feed Fish Only When the Water Reaches Ten Degrees

Fish do not need feeding through winter, and offering food too early is one of the most common mistakes in spring. Wait until the water has held steady above ten degrees Celsius for several days — a floating pond thermometer costs very little and takes the guesswork out of it. At that point, start with a light wheatgerm-based food, given once a day and only as much as the fish clear in a few minutes.

Temperatures can easily drop again in March and April, so pause feeding during any cold snap. Uneaten food sinks and rots, and because the filter bacteria are still waking up, the pond cannot cope with the extra load. Small and often is the rule until the water is reliably warm.

Look After the Wider Wetland Wildlife

A healthy pond is more than water and fish. Frogs, toads, smooth newts and a dozen species of dragonfly and damselfly rely on garden ponds, and spring is when they need the least interference. Never move spawn between ponds, as it spreads disease and invasive plants, and leave an area of rough grass and a log pile nearby for amphibians to shelter in.

• Keep one shallow, gently sloping edge so hedgehogs and birds can drink and climb out.
• Avoid chemical treatments for blanketweed; shade, barley straw and fewer nutrients do the job more kindly.
• Test for pH, ammonia and nitrite monthly once the fish are active, and act on any reading that looks off.

Do this quietly and your pond will reward you all summer: clear water, croaking evenings and a garden that hums with life.