To echo what some other people have said, these algae tanks absolutely should not be used instead of trees. If I see a tree get chopped down and replaced with one of these, I’ll be sad and angry. However, these can go in places where trees can’t go, like rooftops. And you don’t have to either wait for a tree to grow for a decade or take a tree from somewhere else to install one. It also serves as both a seating area and can mount a solar panel on top. These and trees both have their place and should both continue to be used.