Answer:
1) Adding plants to an aquarium that has fish in it is important for several reasons. Firstly, plants provide oxygen to the water through photosynthesis, which is essential for the survival of fish and other aquatic animals. Secondly, plants help to remove excess nutrients from the water, such as ammonia and nitrates, which can be harmful to fish in high concentrations. Thirdly, plants provide a natural source of food and shelter for fish, which can reduce stress and improve their overall health.
2) The three things needed by plants in order to perform photosynthesis are light, carbon dioxide (CO2), and water. During photosynthesis, plants use energy from sunlight to convert CO2 and water into oxygen and glucose (a type of sugar). This process is essential for the growth and survival of plants, as well as for the production of oxygen that is vital for the survival of many other organisms on Earth.
3) Plants produce their own food during photosynthesis, which is called glucose. Glucose is a type of sugar that provides energy for plant growth and development. Some of the glucose produced by plants is used immediately for energy, while the rest is stored as starch or other carbohydrates for later use.