Cut the lid and closing flap off a cardboard egg carton with sharp scissors, so all you'll have left is the egg tray.
Fill each egg cup with vermiculite, soil-less seedling medium, compost or potting soil.
Moisten the soil with a spray bottle until the soil is damp but not dripping.
Press one seed into each cup. Sprinkle several small seeds on top of the soil if they are too small to separate, such as lettuce seeds. You can thin them later after they sprout.
Cover the seeds with fine potting soil or vermiculite so the seeds are lightly covered.
Set the seeds in a warm, sunny location.
Water the seeds every day with the spray bottle.
Transfer the seeds to the soil in your aquaponics system when they have at least two leaves on them.