oh man...good question. I would guess it's never too small as long as there's an isolated area for pods to grow and for a deep sandbed (if that's your thing) to sit.

Think about all the mods done to BioCubes...to have a little mini fuge....man I would have loved to have a 4" x 15" fuge area when I had my Aquapod and BioCube....I had something like 3" x 6"!

yes, I think it's worth putting some macro in. Definitely.