Bloons Wiki
Bloons Wiki
"Ghost Bloon (BTD6)" redirects here. For the type of bloon appearing in Bloons Adventure Time TD, see Ghost Bloon.

The Test Bloon, also known as the Invisible Bloon or Ghost Bloon, is a sandbox only Bloon with 999,999 health that was introduced in Bloons TD 6. This effectively infinite health allows players to test a tower's attacks without having to worry about providing a constant supply of Bloons.

The Test Bloon does not spawn naturally and can only appear in Sandbox Mode, using the Bloon simulator. When spawned, the Test Bloon appears an outlined, invisible Bloon that has the same size, shape and speed of a Red Bloon. It spawns no new children if popped, has no parent, and consumes 0 lives if leaked. It does not have Camo, Fortified, or Regrow variants.

Prior to version 34.0, It is actually possible to pop the Test Bloon using the Bloon Master Alchemist. If the Shrink Potion is applied, the Test Bloon will be reduced to a Red Bloon and Bloon Master Alchemist will receive -1 pops. If other insta-kill attacks are used, the Test Bloon will not be popped. The true RBE of the Test Bloon is a complex topic discussed below.

Red Bloon Equivalent (RBE)[]

See also: RBE

Prior to version 34.0, by examining in-game code, it can be seen that the Test Bloon has two different health values, 0 and 3.4*1038. The zero corresponds to the net pop-count observed when a Bloon Master Alchemist Shrinks the Test Bloon, receiving -1 pops. As the Shrink Potion always deals damage according to the formula "RBE - 1", this would confirm the RBE of the Test Bloon is 0. Furthermore, popping the leftover Red Bloon would bring the total pop count back from -1 to 0.

The other value of 3.4*1038 is the functional RBE for Test Bloon. It is largest floating point number representable by the variable used to store RBE in Bloons TD 6's. This number is so large, that any amount of damage is too minuscule to calculate. So even if a Dart Monkey managed to hit the Test Bloon 3.4*1038 times, the Test Bloon would still remain at 3.4*1038 health as each individual hit would be too small to register. This is true for all attacks in the game. As such, the true RBE of the Test Bloon is, in practice, infinite.

After version 34.0, the Test Bloon has 999,999 RBE.


The Test Bloon has a number of other exotic properties.


Bloon Master Alchemist displaying a rare negative pop count as a result of shrinking the Test Bloon.


Prior to Update 31.0, most instakill attacks, like the Bloon Trap would be able to completely pop the Test Bloon revealing an RBE of 9,999,999. However, this was patched, likely to allow for sandbox testing of instakill towers. Now the Invisible Bloon awards pops to the instakilling tower, while proceeding along the track as normal. This pop count varies drastically based on the method of popping. Currently, only the Bloon Master Alchemist can truly destroy the Test Bloon. If the Shrink Potion is used, the Test Bloon will turn into a Red Bloon, awarding the Bloon Master Alchemist -1 pops.

After Update 31.0, the following effects are observed.

  • Druid of the Jungle's vine deals 10,000,000 damage per grab, with +1 damage for the thorn after-effects.
  • Obyn Greenfoot's Wall of Trees ability. Deals 1 billion damage.
  • Bomb Blitz's Ability (Only when lives are lost). Deals 10,000,000 damage
  • Engineer Monkey's Bloon Trap and XXXL Trap can trap one Test Bloon, dealing 1 Million damage.
  • Psi targets the Test Bloon, but does not instakill it, and does not gain pops from their instakill attack. However, at level 8+ the Destructive Resonance (AoE damage) of the attempt will earn pops based on the Resonance damage. When they level up and gain the ability to target multiple bloons, they can target the same Test Bloon multiple times.

After Update 34.0, the following effects are observed.

Prior to Version 31.0, some towers have the means to eventually destroy the Test Bloon single-handedly:

  • Pat Fusty could, at level 17, reliably loop a Test Bloon indefinitely and eventually destroy it.
  • The Druid of the Storm upgrade can loop a Test 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 Test 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 Test Bloon even without stalling it.
  • Ninja Monkeys can knock back the Test 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 Test Bloon and eventually pop it.
  • Glue Gunners with the Super Glue upgrade can indefinitely glue the Test Bloon and eventually pop it.
  • Bomb Shooters with both the Bloon Impact and Missile Launcher upgrades can stun the Test Bloon indefinitely and eventually pop it.
  • Heli Pilots with the Downdraft upgrade or above can blow back the Test Bloon indefinitely and eventually pop it. Using the Special Poperations upgrade helps speed up the process.
  • Super Monkeys with the Knockback upgrade can indefinitely knock back the Test Bloon and eventually pop it.

Since Version 38.0 or so, the Test Bloon can now be killed by all instakill methods again.

Version History[]

Balance changes in terms of affecting popping of the Test Bloon.

  • NERF Test Bloon now has 3.4*10^38 health, rendering it immune to all attacks except the BMA.
  • NERF No longer triggers Retaliation based attacks such as Bomb Blitz.
  • Change No longer costs 1 life upon leaking.
  • NERF [undocumented] Druid of the Jungle and Bloon Master Alchemist separate attack no longer target Test Bloon.
  • BUFF [undocumented] Test Bloon HP now has decreased to 999,999 health
38.0 (?)
  • BUFF [undocumented] Test Bloon can now be instakilled by all methods that can instakill bloons.



  • The Test Bloon is both the strongest and weakest Bloon in the game, with its 2 RBE values of 0 and 3.4*1038.
  • It is currently not possible to spawn camo, regrow or fortified versions.
  • Ironically, the visual appearance of the Test Bloon is much less visible to the player than any Camo Bloon, while all attacking towers (both camo-seeing and non camo-seeing) can see it immediately as if it is a regular bloon.
  • Before version 31.0, leaking this Bloon will only deduct one life, concluding this Bloon has 1 RBE.
  • Prior to the release of Boss Bloons, the Test Bloon was the strongest Bloon in Bloons TD History. This is the strongest poppable bloon (other than Elite tier 5 versions of Boss Bloons) and technically the poppable 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.
    • Starting on round 750, fortified BADs will have more than 10 million HP. However, they are not poppable, as they cannot be stalled and move at twice the speed of pink bloons.
  • 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, which would be 18,446,744,073,709,551,615. 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.