For a water garden to be the most attractive feature of your garden, it is very important that you establish and maintain a balance within the pond. It is true that submerged oxygenating plants have a great influence on the condition of the water,
but it is not the oxygen they produce that keeps the pond in balance. But, it is in fact the competition that plants provide for the algae which invade ponds as soon as water is warmed by spring sunshine. Algae thrives in water rich in mineral salts. Only when competition is provided for the mineral salts will there be any chance of algae coming under control. For an even balance to be achieved at least one-third of the surface area of the pond should be covered by plants such as water lilies or free-float aquatic plants.
Now that the cooler weather is here and the amount of daily sunshine is minimal, the risk of algae discolouring your water garden is low. But, it is still worthwhile spending time now ensuring that your pond has the correct amount of aquatic plants to use up the mineral salts in the water before algae have a chance to grow and thrive when the warmer weather approaches.