Ground Zero is the final upgrade of Path 2 for the Monkey Ace. It costs $11900 on Easy, $14000 on Medium, $15120 on Hard, and $16800 on Impoppable. The Ground Zero ability is similar to the Super Monkey Storm. It wipes out all regular bloons, and deals 350 damage to MOAB-class Bloons (350 damage is enough to wipe out MOABS, but it won't completely destroy MOABs in very late rounds). It is very useful for taking out tight bunches of bloons or bloons that look like they're getting away. Use it for emergencies. This upgrade changes the color of the Monkey Ace from gray to black.
The only real differences between the Ground Zero Ability and the Super Monkey Storm discouting the damage is that Ground Zero costs a large amount of in-game money and is reusable like other Special Abilities, without having to pay 50 to use it. Although this ability can deal a significant amount of damage to ZOMGs, it is advised to pop the ZOMG layer before using this ability if possible.
As of April 2, 2013 the damage dealt by Ground Zero has been nerfed to 500. Prior to this update, the damage dealt by Ground Zero was enough to instantly destroy BFBs, but ZOMGs were extremely resistant to the Ground Zero.
As of an even later update, on September 26, 2013, it has been nerfed again. The ability deals only 350 damage.
Oddly enough, the Monkey Ace doesn't get any pops from using this ability (The pop count does not increase when the Monkey Ace pops bloons using the ability.)
A common abbreviation for Ground Zero is "G0" or "GZ".
You still get money from bloons popped by this ability.
Ground Zero has the potential to give heaps of money, as when a super-packed mass of MOABs are destroyed by the ability, the resulting payoff can give as much as $10000-$50000, making Ground Zero potentially more effective than spamming Supply Drop. However, it gets useless after a while in Freeplay Mode, as MOABs gain more and more health as the player progresses through higher rounds. Ground Zero will only pop the outer layer of the MOAB, leaving the ceramics behind. (This has been tested on Android).
2 (properly timed) Ground Zeros can complete the MOAB Madness challenge.
This tactic can be used over and over for fast XP (and money on Mobile).
A Ground Zero will pop a D.D.T., but the CamoRegenCeramics inside will survive the blast because it has 350 health and the bomb does 350 damage.
Currently, there is a bug in Bloons TD5 Mobile which makes Ground Zero give more money than it should when used against ceramics. A possible reason for this is the 10 hits required to fully pop a ceramic bloon's outer layer.
It will take 2 Ground Zeroes to beat a BFB (not the children) and 12 to beat a ZOMG (the children will affect with 200 damage).
It takes 15 to destroy a whole ZOMG and 3 to destroy a whole BFB.