Hydroponic gardening is growing in popularity among home gardeners because of the higher quality and higher output it produces. While seedlings purchased from a nursery can be a good start to your hydroponic garden, they might introduce pests or diseases. Starting your own seeds allows you to manage your garden from the beginning.
Choose starter cubes. These cubes are made of inert material and provide support for the plant's roots. They should retain some water without remaining soggy; organo cubes or rock wool work well. Use caution if working with peat pots; this material tends to retain too much water and can drown your seeds.
Prepare your starter cubes. This process will vary depending on the type of cubes you're using. Soak organo cubes and peat pots with water that has a pH of 6.0 to 6.5. Use a liquid pH adjuster to achieve the correct level. Saturate the cubes, then allow them to drain.
Rock wool naturally has a higher pH than the other starter materials; prepare rock wool cubes by soaking in water with a pH of 5.0 to balance the overall acidity level for the seeds. Soak the rock wool for 24 hours, then allow it to drain.
Use the tip of a pen or similar-sized object to make a hole in the top of each cube if they did not come with holes. The holes should be about a quarter- to a half-inch deep. Place seeds in the holes and cover by packing some cube material over them. Keep the starter cubes moist but not saturated and don't let them sit in water. They do not require light until the seeds sprout and don't need nutrient solution until the first true leaves form.
Mix your nutrient solution according to the manufacturer's directions. Dilute the solution to half strength for new seedlings until they are 2 weeks old, then start feeding them at full strength. Monitor the pH level of the nutrient solution and use pH adjusters as necessary. Acidity requirements vary by plant; 6.0 to 6.5 is a good starting point for all growing media except rock wool. Use a solution adjusted to 5.5 to 5.8 if you're growing your plants in rock wool. Keep the growing medium moist but not saturated with solution.
Transplant your seedlings when their roots begin growing out of the starter cubes. Plant the whole cube with the seedling in the permanent growing medium of your hydroponic system.