I use glass covers that I make myself. Have a local hardware store (not a big box one) cut glass to the size you need. Take a glass cutter and cut off a corner or two so that cords and airline can get into the tank (don't make they too big). Then get a piece of fine floor sanding paper, 100 or 150 grit (it holds up well) and sand the edges. I do this outside because of the dust and wearing a mask is a good idea but I don't. You will need a pair of leather gloves. Once sanded rinse and dry. These are easy to make and last a long time if you aren't clumsy like me.
I also have water lettuce on the surface of many of my tanks. You need moderate to high light for this plant to do well but water lettuce is great for removing waste from the water and the roots give the fish something to pick at.