labifleanswered grow question 6y ago Hey gardener! I don't think the size of the cubes is important in my opinion as long as the roots don't see light and have nutrients, it should be fine. After that, it's true that if your cubes are really big, the roots will grow more inside and see less light, and they'll also dry out slower than the small cubes, but it's the same for any small pots of soil. Good luck to you!