Bloom cankers are part of a viral infection spreading across Zezura in Subnautica 2, and they cannot be cut, shot, or smashed open with any standard tool. The only way to break them is the Sonic Resonator, a sound-based device that disrupts Bloom growths and certain mineral clusters. If the prompt to clear a canker never appears when you swim up to one, you are either missing the tool entirely or holding the wrong item.
What a Bloom canker is
Bloom is a bacterial parasite that infects host organisms and seals off parts of the map. Cankers are the swollen, white growths that sprout from infected wildlife and terrain. Alongside them, you will see Bloom biofilm covering cave mouths, Bloom sap blocking oxygen pockets, and free-swimming Bloom parasites. All four respond to the same tool.
Brute force does nothing. The infection has to be broken up acoustically, which is why the Sonic Resonator is gated behind a short story beat before you can clear any infected zone.
Get the Sonic Resonator first
The blueprint unlocks by scanning a discarded Sonic Resonator near the Blackbox - Wander signal. Noa hands you the coordinates after you investigate the wreckage at the Blackbox - Ruby signal. The tool sits inside an open box on a table, near a cave entrance sealed by Bloom biofilm.
Once scanned, craft it at any Fabricator with the following materials.
| Component | Quantity |
|---|---|
| Basic Battery | 1 |
| Wiring Kit | 1 |
| Titanium Ingot | 2 |
| Lead | 2 |
How to destroy a Bloom canker
Step 1: Equip the Sonic Resonator from your inventory. The canker prompt will not register if you are holding a scanner, knife, or any other tool, which is the most common reason controller users on Xbox and PC see nothing happen.
Step 2: Swim close to the white, fleshy growth on the canker, not the surrounding rock or coral. Aim the reticle directly at the infected mass until the use prompt appears.
Step 3: Hold the use input until the canker breaks apart. The resonator emits a pulse that destroys the growth in a single channeled burst.
Step 4: Sweep the rest of the area for additional cankers and free-floating parasites. Infected zones contain multiple targets, and the area only counts as treated once every Bloom growth in it is destroyed.
How you know it worked
Your PDA will state that the treatment was successful, and Wander's audio cues will stop pleading for the infection to be fixed. In story-critical zones, clearing all cankers and parasites opens the infected core nearby, which unlocks an adaptation such as Heat Tolerance for surviving hot biomes.
Why the clear prompt does not appear
If you swim up to a canker and nothing happens, run through these checks in order. The Reddit reports of this issue on Xbox Series X almost always trace back to one of them.
| Cause | Fix |
|---|---|
| Sonic Resonator not crafted | Scan the tool near the Blackbox - Wander signal, then fabricate it. |
| Wrong tool equipped | Open the inventory and place the Sonic Resonator in an active quickslot, then select it. |
| Aiming at terrain instead of the white growth | Move the reticle onto the infected mass itself; cankers have a clear glowing target zone. |
| Standing too far away | Approach within melee-tool range; the resonator is short-ranged. |
| Wrong target type | Some Bloom structures are decorative scenery. Look for cankers, biofilm patches, sap, or glowing blue parasites. |
Bloom targets the resonator handles
The Sonic Resonator works on more than cankers. Keeping a charged unit on you also opens up resource nodes and emergency air pockets that are otherwise inaccessible.
| Target | Effect |
|---|---|
| Bloom canker | Destroyed; contributes to clearing an infected zone. |
| Bloom biofilm | Breaks open sealed cave entrances and passages. |
| Bloom sap | Frees blocked oxygen pockets in cave systems. |
| Bloom parasite | Kills the glowing blue free-swimming variant. |
| Copper, gold, lithium clusters | Shatters large mineral deposits for harvesting. |
Working through an infected zone
Each main infected area on Zezura contains roughly four Bloom cankers and parasites. The first area you encounter typically leads into the infected angel comb, where Wander will ask you to save the kids before continuing. The comb cannot be treated until you destroy the cankers in the linked second site to the north.
The second site has Nibbler Mango patrolling nearby. Flares distract them long enough to work uninterrupted, and the same trick applies to the third site, which is guarded by a Marrowbreach. The four parasites there glow bright blue and are easy to spot once the predator is pulled off you.
Once all sites in a cluster are treated, the core opens, and the associated adaptation unlocks, letting you push into biomes that the infection was previously blocking.