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, similar to Road Spikes. The icicles that form on bloons are considered sharp, allowing the popping of White Bloons and Zebra Bloons but not Lead Bloons.
Icicles is relatively useful for thinning out bloon rushes slightly. Alongside being a stepping stone to the much more powerful Icicle Impale, it serves as a helpful tower at decreasing the density of bloon rushes.