32 ounce Dixie styrofoam cups cost about 3 cents each when you buy them by the case. They are tough and can be used over and over. They are 6 1/2 inches deep. The top is 4 inches in diameter, and the bottom is 3 inches in diameter. I have been using them for the last 5 years with good results. In one case, they were used in a floating garden using a childs swiming pool. Large sheets of styrofoam was cut to float on the surface of the pool. Holes about 3 1/2 inchs in diameter diameter was cut into the foam sheets. The 32 ounce cups were set into the holes. The water was circulated by a pump through other parts of the system, so there was plenty of oxygen in the water. Lettuce grew great in the cups. Another system had the 32 ounce cups sitting in a 4 inch plastic irrigation pipe that had water passing through it at regular intervals. Recently, I found that cheap automobile cup holders hold these cups verry well and can be arainged along a fence or verticaly up a post. The latter use is great for growing strawberrys. To see pictures of these cups in use, use the link below and see if they might be a useful addition to your garden equipment.

Here is a link that might be useful: using large foam cups