Frozen Bloons grow sharp icicles that can pop Bloons that touch them.
~ In-game description
Icicles is the Tier 4 upgrade on Path 3 for the Ice Monkey in Bloons Tower Defense 6. It costs $1,700 on Easy, $2,000 on Medium, $2,160 on Hard, and $2,400 on Impoppable.
This upgrade cause Bloons frozen by the Ice Monkey to grow icicles. These icicles pop one layer off any Bloon that touches them, for up to 3 bloons. The icicles that form on bloons are considered sharp, allowing the popping of White Bloons and Zebra Bloons but not Lead Bloons.