Acid Pool is the first upgrade on the bottom path for the Alchemist in BTD6. It allows the Alchemist to create small, short-lived pools of corrosive acid near it to damage bloons when none are within its radius or if the Alchemist misses. When there are no bloons around the radius, the Alchemist will spawn an Acid Pool around its radius every 2.0 seconds. Each Acid Pool can soak up to 5 bloons or last for 7 seconds before disappearing, whichever comes first. It costs $510 on Easy, $600 on Medium, $650 on Hard and $720 on Impoppable.