The controls for Stabfish vary depending upon the device used to play. Stabfish.io was at first a game meant for PC/Mac, but it is now able to be played on mobile devices.
- PC/Mac: The player's stabfish will follow their mouse, and pressing and holding the left mouse button will make the stabfish "boost," or swim faster, in most cases. To remain still, the player must keep the mouse directly over the stabfish.
- Mobile: The player can control their fish with the on-screen joystick, or on the general right side of the screen. They must double-tap to boost, or press the left side with the other hand while moving. Players on mobile cannot keep their stabfish still unless they are pressed to the wall or corner of the map.
To stab an enemy fish, the player needs to hit them with their weapon. The player can bait fish into their weapon's radius by swimming in tight circles, but fish with longer weapons. Spinning is dangerous since the typical fastest spin is still very wide. Beware that attacking from the front will cause the fish with the longest weapon to win, or whoever has the better angle.
Sometimes, using the left mouse button can cause more effects besides boosting:
- If the player's stabfish is in a family with the Master Challenge completed, the boost effects replace bubbles with other shapes.
- The Octopus, when boosting, produces blinding ink.
- The Electric Eel, when boosting, produces ball lightning that induces paralysis.
- The Electric Ray, when boosting at maximum Stamina, produces a ring of eight balls of lightning that also induce paralysis.
- The Snapping Turtle cannot boost, but can instead retract its head and limbs into its shell and become temporarily invulnerable until their Stamina runs out.
- The Pistol Shrimp, when boosting, shoots 3 fire bullets.
- The Mantis Shrimp, when boosting, shoots a ring of fire.