When I germinate seeds for heat-loving plants like peppers and tomatoes, I set the heat mat controller at a suitable level, generally 75 degrees.
These warm-weather plants like warmth as they grow in the greenhouse. Grow lights set at a suitable distance (about 7 inches) from the seedlings provide an acceptable amount of warmth.
Shortly after a seedling has two “true leaves” I put it into a larger pot using a potting medium that I create using the seedling mix as a basis.
The more true leaves that a seedling develops the more moisture that they transpire from the tray to the environment. So the more mature seedlings get, the more care they require in managing irrigation.
For heat-loving plants, which really love extra attention, I provide moisture with water at the temperature of the tray- not cool water from the faucet. An unexpected dose of cold water can send the seedlings into shock, which slows their growth and reduces their robustness.
To provide nutrients to the growing plants in addition to what is in the potting mix I irrigate with (about) a 1% mixture of water with fish fertilizer and liquid seaweed.
To each Simply Juice bottle (1.6 quarts) of water at room temperature I add:
I pour this solution into the tray, allowing the potting medium to soak it up and percolate it to the plant's roots.
Often I use the liquid irrigation solution to provide additional nutrients by spraying it directly on the leaves of plants after transplanting.