tomato's green algi

i grow tomatos in a green house .(not heated), i grow them in pots and place two pots in a grow bag tray, these trays throughout the summer fill with green algi ,is this harmful
to the plant .i have grown them before and they seem ok, but i just want to check.

 

Should be fine for the tomatoes. The algae just have somewhere with plenty of water, food, light and warmth so it just grows. Remove and compost when you decide you have too much or at the end of the season.

 

Thanks NIgel i appreciate that. have a good day.