- Remove the floating pond deicer or other devices you used to keep the ice from freezing over during the winter.
- Reinstall pumps, filters, and lights.
- Check the water pH with a test kit. The correct pH is between 6.8 and 7.4. If necessary, treat the water with a pH adjuster.
- 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).
- Start feeding fish low protein food when the water is 10°C (50°F).
- At 15°C (60°F), start fertilizing plants with convenient tablets. To maximize growth and bloom, fertilize once a month until September.
- Add floaters such as annual Water Hyacinth and Water Lettuce, and 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. Skim the water for an overabundance of such plants as blanket algae and duckweed or trim out a few Lily leaves.
- Remove all faded blooms and yellowed foliage so they can’t decompose in the water. If left, algae will proliferate and potentially turn the water cloudy and green.
- Watch for a brown spot on Water Lily and Lotus foliage. If detected, remove infected leaves immediately and keep the plant growing vigorously by thinning/dividing when necessary.
- Insects that can attack water plants include aphids, Water Lily beetle, China mark moth, and midges. Aphids are the easiest to control by blasting them off the foliage with a garden hose. Fish will consume them gladly. Ladybugs and lacewings are natural predators. If aphids persist, spray with Insecticidal Soap. But use it in moderation if you have fish. China mark moth affects Water Lilies. They cut off a small piece of leaf and form a cocoon on the underside. They can be rubbed off by hand or treated with Bt (Bacillus thuringiensis), a natural and safe form of control. Leaf-mining midges are small, mosquito-like insects that lay their eggs on the leaves of aquatic plants. Larvae are transparent and almost invisible. They tunnel into the leaves and eat the foliage between the veins, leaving visible trails. Remove any leaves that show these trails. Water Lily beetles also lay eggs on foliage. When the grubs hatch, they mine the leaves. Remove these leaves and hose down the remaining foliage. In fall, be sure to remove the dead stalks of marginal plants, as this is where they like to overwinter.
- It’s a good idea to stop fertilizing aquatic plants in early autumn and to continue removing yellowing or dying foliage.
- If you have fish, switch to food that’s formulated for cooler water temperatures.
- As leaves on trees and shrubs turn color and start to drop, cover the whole water garden with protective black mesh netting. It will keep leaves from falling into the pond. If leaves are allowed to accumulate in the bottom and decompose, algae will be a huge problem the following spring.
- Scoop or vacuum accumulated debris from the bottom before winter.
- Also, remove pumps and electrical equipment.
- Never drain the water. A pre-formed, rigid pool without water can crack or warp due to the freeze/thaw cycle. Or it can heave itself right out of the ground without the weight of the water to keep it securely anchored. A water garden formed with liner needs the water to retain its shape, maintain beneficial bacteria, and help over winter 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.