100s & 1000s tomatoes

Sorry to ask more questions but am wondering what would be the smallest sensible container size I can get away with for Gartenperle (or other similar types)? I have a couple that are about 20cm tall now that really need repotting and have another tray that have just germinated - think I may have sown far more than we need..

Bear in mind that the depth of the container matters as well as the width of it. Hanging baskets are quite shallow so they won't hold much compost unless they're pretty wide, which means less food and less water for the plants. With a pot or tub, which is deeper, you won't need such a big size.