Green water is caused by a mono cellular algae. It thrives in water which is rich in nutrient and also in sunlight. As you sprinkle Aquaplancton powder onto your green pond it will turn a paler, milkier green at first, but then as it filters its way down through the water it latches on to the algae and takes it down to the bottom. Once it is on the bottom, it will start to stimulate the beneficial aerobic bacteria which will multiply and spread, they then consume the algae and any nutrition, like rotting leaves or fish excrement.
Some ponds only need one dose and they become crystal clear, other ponds may need to repeat the dose. On average, small ponds should be treated 2 or 3 times a year in spring, summer and autumn. Larger ponds and lakes are a lot more stable and only need the initial dose once. Aquaplancton is then active in the water for at least a year. The activity doesn’t suddenly stop, but it does begin to slow down so, what we normally say is that if you are pleased with the result and you don’t want it to get back to the way that it was, if you just give it a smaller top-up dose, about a third of the initial dose at the end of the year or the following spring, just to keep the whole process ticking over.