The best container for a Deep Water Culture (DWC) hydroponic system is one that is lightproof, durable, and large enough to accommodate the plants you wish to grow. Here are some factors to consider when choosing a container for your DWC system:

1. Lightproof: The container should be opaque or otherwise lightproof to prevent the growth of algae and other light-loving organisms in the nutrient solution. While algae wont ruin your grow it does move you away from an ideal growth patterns. Those pesky algae eat the nutrients intended for your plants.
2. Durable: The container should be sturdy and able to withstand the weight of the nutrient solution, plants, and growing medium. Some of the cheaper plastic bins deform when filled with water and that is a disaster waiting to happen.
3. Size: The size of the container will depend on the number and size of plants you wish to grow. A larger container will provide more stability and allow for a greater volume of nutrient solution, which can help to maintain more stable pH and nutrient levels.
4. Shape: The shape of the container can also affect the stability of the system. A rectangular or square container with straight sides will provide more stability and prevent tipping, while a round or tapered container may be less stable.
5. Material: The material of the container can also impact the pH level of the nutrient solution. Avoid using containers made of materials that may leach chemicals or alter the pH of the solution, such as metal or some types of plastic. Food-grade plastic containers or those specifically designed for hydroponic use are often recommended.

Common types of containers used in DWC hydroponic systems include plastic storage totes and 5 gallon buckets.

Ultimately, the best container for your DWC system will depend on your specific needs and preferences, as well as the plants you wish to grow. Plastic bins from companies like Rubbermaid work well but a 5 gallon bucket can support a pretty massive tomato plant or two.