A Beginner's Guide to Garden Pond Maintenance

The Balance Is Everything

A garden pond is not a fish tank. It is a small, self-contained ecosystem, and the secret to keeping it clear and healthy is not chemicals or constant cleaning — it is balance. Most of the problems that send people reaching for the phone, from pea-soup green water to smelly black sludge, come down to two things: too many nutrients and not enough oxygen. Leaves, fish food, tap water and fertiliser runoff all add nutrients. Plants and moving water take them out.

Get that balance roughly right and a small pond will look after itself for most of the year. What follows is a simple seasonal rhythm that works for a typical British wildlife pond of a few square metres, whether it holds a handful of goldfish or nothing but frogs and newts.

Spring: Waking the Pond Up

Once the water edges above about 10°C, usually in March or April, everything starts moving again. This is your busiest few weekends of the year.

• Net out dead leaves, twigs and silt before they rot. Work gently — frogs and newts may still be in the shallows.
• Trim dead foliage from marginal plants, cutting just above the new shoots with sharp secateurs. Never cut below the waterline at this time of year.
• Divide overgrown clumps of iris, mint and waterlily every few years. Repot into aquatic baskets using loam-based compost, topped with a layer of gravel to stop it clouding the water.
• Clean the pump and filter. Rinse filter sponges in a bucket of pond water, never under the tap, because chlorine kills the beneficial bacteria that do the actual cleaning.
• Begin feeding fish lightly with a wheatgerm food while the water is still cool, and only give them what they clear in a few minutes.

Summer: Clear Water and Tidy Edges

Warm water holds less oxygen, and strong sunlight plus nutrients equals algae. A little shade and a lot of plants are your best defence.

• Aim for between half and three-quarters of the surface covered with floating plants such as waterlilies — but always leave at least a third of the surface open so gases can exchange.
• Thin oxygenators like hornwort and elodea so they do not smother the pond. Drop the trimmings on the bank for a day so any small creatures can crawl back in.
• Top up with rainwater from a water butt. Tap water brings phosphates and nitrates, which is exactly what the algae want.
• Run an aerator or fountain overnight during hot spells, when oxygen levels are at their lowest and fish are most at risk.
• Deal with blanketweed by twirling it out with a cane or rake, rather than reaching for a chemical treatment that will knock the whole ecosystem sideways.
• Deadhead flowers and remove yellowing leaves promptly, before they sink.

Autumn: The Leaf Battle

The season you handle badly in October shows up as green water next May. Fallen leaves are the single biggest source of unwanted nutrients.

• Stretch netting over the pond in early autumn, before the leaves start falling. It is the cheapest, easiest job in this whole guide, and it saves hours of skimming.
• Skim daily during heavy falls with a long-handled net. Do not wait for the leaves to sink.
• Cut back marginal plants, but leave some seed heads standing for insects and birds, and do not cut below the waterline as the weather turns cold.
• Stop feeding fish once the water drops below 10°C — their digestion slows and uneaten food just pollutes the pond.
• Do leave a layer of silt and a few leaves at the bottom. Frogs, newts and dragonfly larvae hibernate in that mud, and a spotless pond is a lifeless one.

Winter: Quiet Vigilance

For most of the winter, the less you interfere the better. A few small habits keep things safe through frost.

• Keep a hole open in the ice so gases can escape. Float a ball in the pond, or use a small pond heater. Never smash the ice — the shock and pressure waves can kill fish.
• Keep a pump or aerator running, but switch off fountains and features during hard frost to protect the mechanism.
• Clear leaves from the netting after storms, so it does not sag into the water.
• Check the pond after long freezes, and top up levels with rainwater if evaporation or splashing has dropped them.

A Simple Kit and a Few Golden Rules

You do not need much: a long-handled net, sharp secateurs, a bucket kept for pond use only, a pair of waders or wellies, and some aquatic baskets and loam compost. That is genuinely it.

Beyond the kit, three habits carry the most weight. First, always use pond water, not tap water, when rinsing filters or cleaning anything. Second, never use insecticides, weedkillers or fertilisers near the pond, and leave a wild, untidy margin of long grass — that strip is where frogs, hedgehogs and insects shelter. Third, add a gently sloping edge or a short ramp of stones so that wildlife which falls in can climb out.

Do those things, keep the leaves out, and your pond will reward you with frogspawn in February, damselflies in June and a patch of water that hums with life all year round.