Seasonal maintenance tasks
Regular maintenance tasks will help you avoid many pond problems.
SPRING: Run the pump and check connections and hoses for any leaks. Vacuum the pond bottom if sludge has built up past 2.5 centimetres, but a complete clean-out is not an annual necessity unless you've had problems. Don't empty the pond and refill it with fresh water, as this provides additional nutrients for algae.When it's time to return plants to the pond, first place them at a shallower depth than their final location in order to encourage faster growth to beat out the algae for nutrients. If you are potting up new plants, Lascelle recommends using a clay-based soil with a layer of gravel on top to avoid adding silt to the water.
SUMMER: Use pelletized aquatic plant fertilizer (sprinkling fertilizer on the surface feeds the algae). Overfeeding fish also encourages algae. Remove any spent blooms or yellowing leaves. Keep up with evaporation loss so you are not adding too much tap water at a time. Make sure landscaping surrounding the pond is not draining into it.
AUTUMN: If the pond is surrounded by deciduous trees, use a net to keep leaves out. Clear out dead foliage before winter. As plant material disappears and snails and fish become less active with falling temperatures, expect algae to become dominant, and be aware that major cleaning will only encourage its growth by providing extra nutrients.
WINTER: Decaying plant matter may produce toxic gases, so keep a hole in the ice open for the health of any overwintering fish. You can use a floating de-icer or, if practical, lift your pump up to the surface where it will bubble and keep a small area open. Don't use a hammer to open a hole in the ice, as you can actually concuss the fish. Sit a pan of hot water on top to melt through instead. Pressure from expanding and contracting ice can damage the pond wall or liner. For ponds with no fish, float a ball or log on the surface.