Water Garden Maintenance

August 31, 2021

All gardening requires a degree of on-going maintenance. Installing a water garden does not necessarily mean endless hours of work per week.

Choose an area on your property that receives at least six hours of direct sunlight per day if you intend on having flowering aquatic plants.
Be sure the site is level and not at the lowest part of the garden where runoff (especially lawn fertilizer) will upset the delicate, natural balance. You can read our pond building guide for more details.
There are two ways to combat algae and permanent green, smelly water: use plants/fish or a biological/mechanical filter.

Check the water level of your pond frequently, especially during periods of hot weather. If it goes down too far, it will cause temperature fluctuations that can adversely affect plants and fish.
When first filling a new water garden, it’s recommended that the watersitfor a week before plants are added. Wait an additional week after that to add fish.
Check all filters in your pond once a week. Less output from fountains, waterfalls, or pumps may indicate that a hose is clogged or the filter is dirty and may require cleaning or replacement.

Adding scavengers such as aquatic snails and tadpoles can help the biological balance in your water garden.
Adding fish to your water garden is beneficial because they eat mosquitoes and other insect larvae as well as some algae; however, too many fish can deplete oxygen, promote algae growth, and reduce water quality.
Stock 2.5 cm (1”) of fish per one square foot of pond surface area (figures are based on the size of the fish at maturity). While common goldfish require very little care, koi on the other hand must be fed regularly, need better filtration, and may outgrow a small water garden. You can reduce the amount of waste from koi by using a low ash fish food.

Remove the floating pond de-icer or any other device you have used to keep the ice from freezing over during the winter. Reinstall pumps, filters, and lights.
Be sure to check the water pH with a test kit; keep in mind that the ideal pH is between 6.8 and 7.4.
Clean out leaves and organic debris that might have accumulated at the bottom over winter.
Move existing hardy plants from the bottom of the pond to their proper depth when the water temperature is 4°C (40°F).
Begin feeding fish low protein food when the water is 10°C (50°F). Start fertilizing plants with convenient tablets. To maximize growth and bloom, fertilize once a month until September.
Add floaters such as water hyacinth and water lettuce as well as new water plants when the water temperature is 18°C (65°F).
This is also a good time to switch to a high protein fish food.

Thin out plants if the water surface becomes too densely covered. Simply skim the water for an overabundance of plants such as blanket algae and duckweed.
Remove faded blooms and yellowed foliage before decomposition; if left, the water could potentially turn cloudy and green due to algae buildup.
Watch for brown spots on water lily and lotus foliage. If detected, remove infected leaves immediately and keep the plant growing vigorously by thinning/dividing when necessary.
Insects including aphids, water lily beetles, and midges can damage water plants.
Aphids are easiest to control by blasting them off of foliage with a garden hose. Fish will consume them gladly, and ladybugs and lacewings are natural predators. If aphids persist, spray with Safer’s® Insecticidal Soap.
Leaf-mining midges lay their eggs on the leaves of aquatic plants by tunneling their way in and eating the foliage between the veins, leaving visible trails. Remove any leaves that show these trails. Watch for water lily beetles as well, as they also like to lay their eggs on foliage.

Conclude fertilizing aquatic plants and continue to remove yellowing or dying foliage.
If you have fish, switch to food that’s formulated for cooler water temperatures.
As the leaves begin to change colour and drop, cover your water garden with protective netting; this will prevent leaves from falling into the pond. Given the chance, fallen leaves will accumulate and decompose at the bottom of the pond, causing algae to form over time.
Remove pumps and electrical equipment before freezing.
Never drain the water from your pond. A water garden formed with liner needs the water to retain its shape, to maintain beneficial bacteria, and to help overwinter hardy plants and fish.
Install a pond heater or bubbler to keep an area of water from freezing so oxygen can continue to be available to fish and toxic gases, like methane, can escape.

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