Bloptonite

Bloptonite is a type of radioactive blop that first appears in Level 59 in Bloons Super Monkey 2 Mobile. When collected by Super Monkey, Ice Monkey, or Storm Monkey, movement is slowed. The effects of accumulating Bloptonite stacks, making it more difficult to move depending on the amount collected. When the Bloptonite meter is full, the monkey moves at TBA% of his original speed.

Recovery
To recover from Bloptonite, you must tag out. When tagged out, the Bloptonite meter (shown below the Tag Out button) will deplete over time at a rate of TBA% per second.

Monkeys from powerups and epics (e.g. Crouching Monkey, Parallel Universe clone), allies, and Doctor Monkey as a playable character are completely immune to Bloptonite.

Strategies
A great guide on the forums is right here if that's what you like to read.

It's dangerous to go alone!
If you only have one monkey, the Bloptonite meter will not go down, and can make it very difficult to complete the level. This becomes even more important if the player wants to get Ice or Storm badges.

Don't get distracted by blops!
If choosing between being safe from Bloptonite and collecting Blops, choose being safe from Bloptonite. If you want the blops, enter the level with a Tier 3 or 4 Blop Magnet.

Keep a mental map, and avoid the unavoidable
If you can keep track of when and where Bloptonite appears, you can be ready when it does. As a rule of thumb, Bloptonite come from the edges of the screen and generally move downwards as the level goes, so the player should try to stay in the middle of the screen to buy more reaction time.

Should you end up in a case where contact is unavoidable, you can:

Target the area where there is the least Bloptonite and fly through

OR

Tag out, wait for the Bloptonite to pass, then tag back in

Take out the source
Most areas of Bloptonite come from a source, and stop as soon as it is popped. So, target it!

It is advised to diversify the number of directions that you fire weapons, as some targets can become tricky when only using forward-firing weapons.

Trivia

 * Bloptonite's name is most likely a reference to Kryptonite, a material in the Superman universe that weakens Superman when exposed to the material's radiation, similar to how it weakens Super Monkey and the other monkey's flying abilities.
 * This is also likely true due to the fact that Dr. Monkey is immune to the effects of Bloptonite, similar to the fact that Kryptonite radiation is harmless to humans.
 * Though in this case, he is actually wearing the Anti Bloptonite Cloak to become immune to Bloptonite. Additionally, he is not immune to negative effects himself in Bloons Adventure Time TD. This confirms that Dr. Monkey does not really possess negative effect immunity naturally, possibly even Bloptonite, and Bloptonite may be a type of radiation affecting all life forms just like the ones in real life.
 * Fortunately, Bloptonite, unlike blops, do not get drawn towards the monkey or Tier 3+ Parallel Universe clone, even when equipping Blop Magnet.
 * They do not bounce on the edges of the screen either.
 * Invisibility Cloak cannot make the monkey phase through Bloptonite.