Bloon Trap captures Bloons until full. Select to empty full trap for cash.
~ BTD6 description
Bloon Trap is the final upgrade of Path 1 for the Monkey Engineer in BTD5. It costs $2975 on Easy, $3500 on Medium, $3780 on Hard and $4200 on Impoppable. Once bought, the Engineer will automatically deploy a Bloon Trap around any part of track within the Engineer's own radius. The Bloon Trap will make bloons that come over it be destroyed entirely, though no money is awarded for each individual bloon consumption. It does not destroy MOAB-class bloons or Camo bloons (except in BTD5 Mobile), which fly over it, unlike spikes. It can hold up to 250 RBE worth of bloons. Once full, the rims of the Bloon Trap will flash blue and magenta, prompting the player to collect it for twice as much cash as the bloons would normally give. If the player does not collect the Bloon Trap after a certain while, it auto collects, giving less cash than manual collection. Only one trap can be active per Monkey Engineer.
In BTD6, this upgrade returns as the fourth upgrade of Path 3 for the Engineer Monkey. One Bloon Trap can be deployed on the map around the nearest track near the Engineer's own radius (like Smart Spikes on Close setting). Bloons that come over it are trapped inside, though no money is awarded for individual bloon consumption. MOAB-class bloons and Camo Bloons (unless granted camo detection prior to deploying) will simply pass right through the Bloon Trap, as per usual. It can hold up to 500 RBE worth of bloons (530 with Bigger Traps). Once full, the Bloon Trap will shake to the left and right and emit an off-white colored aura. Like in BTD5, if the trap is collected manually, the player gets twice as much cash as the bloons would normally give; if not collected within 15(?) seconds, or the Bloon Trap is upgraded to XXXL Trap, it will autocollect itself for only the original cash amount as if all bloons were popped normally. Only one trap can be active per Engineer Monkey per round; a new Bloon Trap will be replenished after the current round ends if the trap is absent, and only two traps can be deployed per engineer each round (this is not the case for XXXL Trap).
The Bloon Traps yield less money as the rounds go higher in the online versions, however, Bloon Traps always yield the same amount in the mobile version. Thus it is more worth it to buy Bloon Traps in the mobile versions than it is in the online versions.
In Bloons Monkey City Flash, it starts to dramatically lose value after Round 15, where the value of Bloon Traps reduces to 65% of its original value. After Round 22, it drops again to 20% of the original value. After Round 27, it drops to a tiny 5% of the original value.
In BTD Battles mobile, Bloon Traps engineers are less effective against Grouped Normal Rainbows than Rainbow Regen Rushes for the exact same price. This is because the Cleansing Foam can de-regen the regen bloon property while the Bloon Trap can trap the de-regened Rainbows. Grouped Normal Rainbows, however, are completely unaffected by Cleansing Foam, while Bloon Traps cannot easily trap more than 10 Rainbows per trap.
In Flash, Bloon Traps cannot be used for regen farming. After filling up Bloon traps from the same engineer twice, the next bloon traps yield no money whatsoever.
Try to collect Bloon Traps manually as often as possible, as Bloon Traps do not profit when collected automatically. Additionally, no money is earned when bloons enter, and thus cannot return any money until collected.
There is a 3-second cooldown before the next Bloon Trap can be spawned.
This upgrade allows sentries to pop Lead and Camo bloons, likely a bug.
Bloon Traps can be saved in save files. Therefore, they will not disappear when the game has been quitted and re-loaded again.
In BTD Battles on iOS and Android, if you sell a Bloon Trap Tower, its trap, if still not full, will still be there and still trap bloons.
On older versions of BMC Mobile in the SD (small device) version, the Bloon Trap will glitch out and flash continuously for several seconds after multiple Bloons get captured by it, even after collected. This issue has since been fixed.
Prior to a recent update for BMC Mobile, this can trap D.D.T.s, giving 16,656 cash, or 33,312 cash if emptied manually.
This has predated the XXXL Trap's ability to trap MOAB-Class Bloons in BTD6, including D.D.T.s, other than the B.A.D.
Although traps always explode eventually, Monkey City claims that every trap is sent to the Bloon Containment Unit to safely dispose of all the trapped bloons. Unless the explosions are really animations of traps warping to the Unit offscreen, this is a self-contradictory scenario.
In BTD6, it shows the engineer either standing on the trap, or violently kicking it.
In BTD6, it makes an eerie electronic humming sound every time it traps a bloon inside.
In BTD6 before update 12.1, if a Bloon Trap Engineer was affected by Gwendolin's Heat it Up ability, the game would crash.
Similar to BTD Battles, if the Tower is sold in BTD6, the trap will still remain on the ground and keep trapping bloons. But sometimes it will try to find a newly placed Bloon Trap Tower as if the trap is created by the tower. So the new Engineer cannot generate a new trap unless the trap on the ground is filled, and the pops by the trap will be counted to the Engineer.
A Monkey Knowledge Point called "Big Traps" increases the RBE limit to 530, but it erroneously states it can hold 280 RBE.
This has been fixed in the 13.0 update.
As of Version 13.0, the description was changed from "... Tap to..." to "... Select to...", so as to provide a device-neutral description for the Bloon Trap upgrade.