1. Hi. I grow swamp plants, and need to have the soil box inside a box filled with water. But I recognize that the water develops an odor, and wonder if it makes sense to do something about it, and if, how and what to do. I don't want the plants to suffer, but I want to get rid of the foulish smell of the water. 2. Also, I see that much of the white sand and white stones become covered with a light green algae or something like that. If I would decide (not sure yet) to get rid of the green algae, how best to do this?