Hey halfway, the air-stone is a redundancy in an
ebb and flow system that is setup correctly.
When you drain an Ebb and Flow system, it creates a tiny vacuum in the grow chamber that pulls ambient air into the chamber all the way to the very bottom.
Timing your drain cycle to supply the proper amount of air is the key. The drain cycle should be as often as possible within reason, both botanically and financially. Too often and it doesn't really help but will use electricity.
The timing depends on ambient conditions of course. If it's very hot out, you'll have to increase your floods to compensate for the heat and to keep the roots at the correct temps. When it's cooler, not as many floods are necessary.
Here's what makes some ebb and flow people crazy when I say it; I use a one hour on/ two hours off cycle, 24 hours a day, 365 days a year. I've done so for more than 20 years on all my plants and they simply love it.
This timing provides maximum
nutrients, maximum water and maximum oxygen to the roots while keeping them cool even on 100 degree days.
During the drained cycle, the plants still have plenty of water due to the retained water within the media. This is why using a porous media like hydroton is so very important.
It takes the plant much more time to use all the oxygen that is pulled into the growing chamber each two hours. There will be plenty for all the plants needs for the entire two hours of being drained and if the proper media is used, there is plenty of water also for the herringbone roots to absorb.
Having a properly sized grow chamber is absolutely necessary for the above reasons. Too small and not enough root space, water retention or oxygen is supplied to the root zone.
You really can't go too large. The roots will expand to what they need. If you use a grow chamber that's the size of Detroit, the roots will stop long before reaching the city limits.
With all hydroponic gardening, timing, timing, timing is the most important factor in it's proper use.
Many hydroponic growers will insist that a 15 minute flood is proper. I've proven that it doesn't work as well as my one hour flood with a two hour drain cycle. That's why I've used it for all this time after trying many, many combinations.
A 15 minute flood will work. I've found it just doesn't work as well as the one hour flood for me.