Depleted Bloontonium Darts

"Shots can now hurt any bloon type."

- BTDB Steam description

Depleted Bloontonium Darts, referred as Depleted Bloontonium in mobile versions, is the second upgrade for the second path for the Dartling Gun which allows the tower to pop any bloons, including Lead Bloons and Frozen Bloons. The upgraded darts that the Dartling Gun shoot appear the same as normal darts, unless in BTD5, where they gain a green wavy border around the projectile. Oddly, a Laser Cannon without this upgrade cannot pop Lead Bloons, but a Ray of Doom can regardless of this upgrade. The Dartling Gun changes its color to purple and it gets a radioactive symbol on the top of the gun when upgraded to Depleted Bloontonium Darts, which disappears if any tier-3 upgrade (or the Faster Barrel Spin upgrade sometimes) is bought.

It costs $850 on Easy, $1000 on Medium, $1080 on Hard and $1200 on Impoppable.

Summary
Depleted Bloontonium Darts is an expensive upgrade, but it allows the Dartling Gun to reliably pop Frozen and Lead. It is generally not a worthy upgrade unless countering DDTs or Dreadbloon: Armored Behemoth, as other options for countering Leads are usually better. It may be useful when adding Ice Towers, however.

Tips

 * Add it to an already upgraded Dartling Gun to make the most out of the bonus lead-popping power.

Trivia

 * Starting from the Halloween update of BTD5 Flash (late October, 2013), the Bloontonium Darts will now glow green.
 * Depleted Bloontonium has the similar effects as the real-world depleted uranium, yet is closer to plutonium in name; depleted uranium bullets catch fire on impact.
 * In Bloons TD 5 Mobile, the name of this upgrade excludes the word darts because the name would be too lengthy, even on the HD version.
 * It's useless on the Ray of Doom because they can already pop Lead Bloons. However, most people would normally upgrade to Depleted Bloontonium Darts before the Ray of Doom because Ray of Doom is too expensive.
 * This upgrade is one of the few upgrades to not return in BTD6.