Square net pots?

[pengyou]

Are there square net pots? I have seen larger ones - about 1 gallon size, or half gallon size. The reason I ask is that if I used square net pots I could put more plants in the same space. I know that root size might be an issue...is there some way to train roots to grow downwards rather than fanning out? Maybe by causing more flow in the nutrient - having deeper pots and more current?