* Plants: Live plants in a fish tank are the primary producers of oxygen. They use photosynthesis, a process where they convert light energy into chemical energy, and in the process release oxygen as a byproduct.
* Water: Water itself doesn't produce oxygen, but it's essential for plants to carry out photosynthesis.
* Snail: Snails are beneficial for cleaning up algae, but they don't produce oxygen.
* Rock: Rocks don't produce oxygen. They provide a substrate for plants and can also help create a visually appealing environment.
Important Note: The amount of oxygen produced by plants depends on factors like the type of plant, the size of the tank, and the amount of light.