Algae and blanket weed thrive in acid conditions. Aquaplancton neutralises any acidity, raising pH levels causing algae and blanket weed to die out naturally.
Acidity is caused to some extent by rain, because all rain is acidic to a greater of lesser degree. However, the main culprit for acidity is fallen leaves.
Oak leaves, Pine needles, Acers, Plum or Flowering Cherry trees are particularly acidic. Aquaplancton will eat away any fallen leaves, neutralising any acidity and raising pH levels favourable to aquatic life.
If your pond is alkaline with a high pH, you can still used Aquaplancton, in these cases the pH usually stays about the same.