The amount of light required in growing lettuce hydroponically may differ from plant to plant. In the case of most indoor hydroponic systems, your plants need more artificial light in order for photosynthesis to transpire. If you do not have enough artificial light yet, get grow lamps like LED lamps which generate the right intensity of artificial light without the additional heat. You could try an 80-watt fluorescent light, and keep it five to seven centimeters away from your plants, to encourage optimum growth, and allow around 18 hours of light each day.
There are a lot of hydroponic nutrients that can help your lettuce plants not only grow big and healthy, but also enhance their quality so that their leaves will become green and crisp. Also, you have to take into consideration the pH level of the water you’ll use, as the hydroponic nutrient solutions you add to the water will affect the pH level. Water pH level for lettuce plants must be between 6 and 6.5. Salts and nitrate nitrogen are both recommended nutrients for growing lettuce plants the hydroponics way.
Water temperature for growing lettuce plants is between 68 to 75.2 °F (20 to 24 °C), and you can monitor this in your grow tray. You can make use of a submersible heater. It can help you maintain and regulate the right temperature. You can lower the room temperature using oscillating fans. Doing so will help avoid tip burn in your lettuce plants, and at the same time keep humidity in the growing room a lot more regulated.