Bloons Tower Defense 5 - Daily Challenge May 20, 2013 (Farming Extremist...

I used the Dartling Speciality Tier 1, but I believe you can beat it without just you have to be really quick on upgrading the farms. Use "," and "." for quick upgrade hotkey.

Farming Extremist - 4/x Dartlings are the only tower that can pop lead bloons. Rounds 30-60. Leads are zebras, and MOABS/BFBs are leads. Prepare for round 46/50. By Jlm7 & Kim Davis

Video is on 3x speed
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(Please comment if you have better strategy)
For more walkthrough: http://bloons-tower-defense-5.blogspot.com