My current mana gen setup is a 5x5 square in the ocean with hydroangeas at the corners and an alternating line of mana spreaders and mana pools in the center. Once the mana gets to the surface, I move it with recessive and dominant sparks (and the occasional mana spreader to a couple pools I don't use often enough to warrant sparks). In theory, it could be upgraded to really churn out the mana, but for my needs it's more than good enough.