This is easy with a system like that one grow rocks are fine.

Make sure your overfill tube is working because you will need it. Ebb & flow in something like this should work for plants up to 24-30" tall plants at finish. That's not much of a yield but if you do enough then it adds up quick. You will find if the plants root system gets too large they will clog the 1" hole you are using as a drain.

That is why I said to make sure your overfill tube is working.

Happy growing

In this Saturdays pod-cast I cover Hydroponics nutrients so you may want to check it out.