I have the Stealth Hydro Bubbleponics system, and my tank is full of roots when I grow. You ain't seem nothing yet. by the time the plants are 12 inches tall, your tank will be full of roots...but that is GOOD. time they get two feet tall, the roots will be two feet long.
I've learned how important Oxegen is and I added an extra air stone, and i suggest you do the same. most instructions say drain and replace every 7 to 10 to 14 days, but for very rapid growth, do it more often. even if you put the same solution back in, they will grow faster cause of the hour or so that there was nothing but air available to the roots. Try it, you['l be glad you did.
If you have the Stealth Bubbleponics system, let me know. I 've had some experience and I learned a lot too.