Since this is a prototype aquaponics system, we've decided to remove the green tea, as they were taking over the grow bed (a friend said they were spearmint plants). Their growth was the fastest and growing on top of others.
We also removed three black-eyed pea plants, as their leaves were getting so large, that they block the light from most other plants.
Next, we bought some Great Lakes California Lettuce seeds. I'd say three tablespoons worth, for 5 Saudi Riyals (US$1.3).
We removed some of the hydroton, sprinkled the seeds, and covered them again. The seed is roughly 4mm (0.16") in length. I know, I know, I should germinate first then transplant it back into the grow bed.. I'm too lazy for that :)