The cheapest, easiest, and most often used containers are big plastic tubs. Most people pick the ones around three feet wide by two feet deep. These are a good size for remaining stable under the weight of the water. They’re also about the maximum size for portability, so if you might need to rearrange your grow room or don’t want leave your plants outdoors for the most part, bringing them in only during rough weather, don’t go any larger.
Directions: Fill the tub about ½ full of your growth medium. Fill it the rest of the way to the top with water. Add in a hose for your aerator and you’re good to go.
Cut half a dozen large holes in the lid of your plastic tub plus one smaller hole to add nutrients. Carefully slide your plants in place so that the roots dangle down into the water. As long as you keep the water oxygenated and full of nutrients, you shouldn’t have to do much maintenance on these simple systems. Go ahead and line them up around your grow room however you see fit. You can usually fit quite a few of these rectangles into a densely-packed space.