The Ghost Bloon is a Bloon that only appears in Sandbox Mode in Bloons Tower Defense 6. It is transparent, with a dotted outline. The Ghost Bloon cannot be encountered in any game mode besides Sandbox Mode; the main purpose of this Bloon is for testing how much popping power a tower has, as well as for testing the activating of 'lost life' upgrades and abilities.
The Ghost Bloon can be destroyed instantly by certain towers, such as the following:
- Druid of the Jungle's vine
- Bloon Master Alchemist's shrink potion
- Obyn Greenfoot's Wall of Trees ability
- Bomb Blitz's Ability (Only when a bloon leaks)
- Legend of the Night's Black Hole (Only when a bloon is about to leak)
- Engineer Monkey's Bloon Trap and XXXL Trap
Additionally, some towers have the means to eventually destroy the Ghost Bloon single-handedly:
- Pat Fusty can, at level 17, reliably loop a Ghost Bloon indefinitely and eventually destroy it.
- The Druid of the Storm upgrade can loop a Ghost Bloon indefinitely and eventually allow the Druid to destroy the bloon.
- The Sun Temple or True Sun God with sufficient magic sacrifices can knock back the Ghost Bloon with its magic shockwave and deal enough damage to pop it quickly relative to other strategies.
- 20 maximally buffed Sun Temples can pop a Ghost Bloon even without stalling it.
- Ninja Monkeys can knock back the Ghost Bloon with the Distraction upgrade, thus creating an infinite loop and eventually popping the Bloon.
- Ice Monkeys with both the Re-Freeze and Enhanced Freeze upgrades can indefinitely freeze the Ghost Bloon and eventually pop it.
- Glue Gunners with both the Super Glue and Corrosive Glue upgrades can indefinitely glue the Ghost Bloon and eventually pop it.
- Bomb Shooters with both the Bloon Crush and Missile Launcher upgrades can stun the Ghost Bloon indefinitely and eventually pop it.
- Heli Pilots with the Downdraft upgrade or above can blow back the Ghost Bloon indefinitely and eventually pop it. Using the Special Poperations upgrade helps speed up the process.
- Super Monkeys with the Knockback upgrade can indefinitely knockback the Ghost Bloon and eventually pop it.
- It is poppable by damaging it 10 million times, but it would be a waste of time to try and do so.
- It is currently not possible to spawn camo, regrow or fortified versions.
- Popping it will give the tower 9,999,999 pops (provided it was not previously damaged).
- Leaking this Bloon will only deduct one life, concluding this Bloon has 1 RBE.
- This is the strongest bloon and the technically the bloon with the most layers. However note that monkeys with 'strong' targeting will target other bloons first, ignoring it until it is the final bloon on screen.
- Having a tower pop roughly 215 of these bloons allows that tower to reach the old maximum pop count of 2,147,483,647 (231−1) which is the higher number that can be stored in a 32-bit signed integer variable.
- As of Version 9.0, the pop limit is now lifted higher than the 32-bit maximum, presumably to the 64-bit maximum. However, it currently is impossible to determine the new maximum number through in-game testing, as attempting to do so will eventually crash the game before reaching the new maximum number.
- The actual name can be somewhat debatable, as the hotkeys menu on BTD6 Steam calls the Ghost Bloon "Test Bloon."