Square pots save space and can help you maximize the square footage of your growing area. 

Square Pots

Square pots are the chosen shape for many hydroponic systems these days, mainly due to the space savings that many small square pots have vs. round pots of the same size. Ideally one could use square pots early in the plant's growth allowing for more plants per square foot. Then as the plants get larger transplant into larger round pots as they are more readily available in larger sizes.