green surfaces

[nemo]

in my poly tunnel the surface of the soil in some of my raised beds is growing a green algae .what am i doing wrong must i increase air circulation or less watering .what do you think
thanks
regards nemo

[Two_Sheds]

less watering, more air circulation
I think it can indicate low fertility and acidic soil too. have a Google

[Patchninja]

It's the main reason why I don't grow in the soil of the gh. I find it's easier to control pots - especially if you have to be absent quite a lot.