Board Thread:Questions and Answers/@comment-69.140.13.179-20140424235312/@comment-20126248-20140425023904

Grouped Pink Bloons. Fastest Cooldown in the game.

Grouped Black Bloons. Slightly Slower Cooldown than Pink Bloons, but gives more income.

Same goes for White Bloons.

Grouped Leads... Very slow cooldown but gives you pretty good bag of income.