The border soil in my greenhouse is covered in moss and a curious flat algae-type plant. I've changed the soil, and keep taking the top layer off as it 'greens' over, but to no avail.. Ideas please? The door is always ajar, and often wide open in an attempt to allow air to circulate, and the windows in the roof are far from airtight even if they are closed. Crops - tomatoes peppers,, cucs, tend to get mouldy - I often wonder why I keep trying - the triumph of hope over experience, perhaps!!