Best use is trolling in CO-OP with 1/3 Ice Towers. (Why 1/3 you ask? I noticed that, even though it doesn't say so in the upgrade description, it seems to make it harder for bloons to past. In sandbox, I made a 1/2 Ice Tower against a couple pink bloons. It stalled them. I did a 1/3 Ice Tower, and it seemed to completely stop them.)
2601:2C1:C001:1F20:C5A0:24B8:F8E:EC16 wrote: If you have two or more right next to each other, covering the same area of track, bloons have virtually no chance of escaping. My friend coined the term, "Ice monkey road block".