Those using Barley Bio Algae Control weekly. In a small pond or container pond should be adding the 10ml measure every week now to control the green water in this weather.
You cannot overdose Barley Bio Algae Control as it is not a chemical - so do not worry that you may be adding too much if you do not know the volume of water in your pond. It will do no harm to fish, plants, pets or wildlife.
To help the balance of the pond or container pond check you have enough rafting plants or waterlily leaves across the surface to give shade to the water and healthy submerged oxygenating plants to use surplus nutrients.