This is the time of year when duckweed and green algae blanketweed may begin to reappear. Duckweed (the 3 lobed leaf with a thread thin root) seeded down last Autumn and will rise up now to threaten to carpet the water surface and should be removed using a dipping net as soon as any piece appears.
Blanketweed is a green algae growth that looks like green cottonwool and can start to grow quickly in the warm weather of late Spring especially if you had large volumes of frog spawn jelly decomposing into the water this month. The Barleystraw product added in February/March should be having an inhibitor effect by now on the green algae growth.
Small amounts of blanketweed will be eaten by the newly hatched tadpoles and the rest will be overcome by waterlilies and other surface cover plants if you have sufficient of them.
Try not to twist the blanketweed around a stick to remove it from the pond as that traps wildlife inside the twist and even leaving it in a pile on the pond side will not allow the creatures to get out. Unravel it and shake it straight away to dislodge the trapped creatures.
Watch out for any other invasive pond plants - 5 aquatic plants are banned in the UK and need to be dealt with carefully if you already have them in your pond.
See our Tips and Advice page for images for identification: Unwanted invasive pond plants