I think clay pebbles are at best of no real value in the bottom, and from reading on the hydraulic interface of two different mediums, water tends to resist crossing such a barrier. My current grow uses no pebbles. i'm also running both coco and soil 3 pots of each, and 2 have AIT units ( similar to airdomes ). I've only turned on the res about 3 days ago, so no real data yet.
So in your view, Autopots need and should not have their medium go through wet-dry cycles, rather the constant small incremental feedings overall keep the coco at a fairly constant moisture (with aerated water), with this the goal. Seems very plausible and likely a major or even the main benefit with Autopots. This and the remarks so far appear to presume that the coco vs. the bottom/Hydroton portion of the pot is where the root growth and activity takes place. But I haven't seen that this has been fully resolved. There has not been much related testing with Autopots reported yet.
A few questions for all Autopot users:
1) In my doing post-harvest root examination so far on a single Autopot pot (too small a sample?), nearly all of the roots were in the bottom/Hydroton portion, not in the coco. This suggests that the Hydroton layer is what we should be most concerned with, not the upper coco layer. How does this fit in (or not) with the presumption that fairly constant optimal coco dampness is what is desired, and the perhaps related presumption that the roots grow mostly in the coco?
2) Can anyone contribute any observational information on these matters? For example, has anyone else yet done a post-harvest examination of Autopot roots? Were the roots in the bottom/Hydroton and/or in the coco?
3) Would Autopots work even better if some real wet-dry feeding cycling were added? Autopots, on their own, look to do rather well at constant incremental feeding to maintain consistent media moisture/wetness. Would adding some wet-dry cycling improve the grow? For example, why not say once or twice per week close off all your valves (for a day, 2, whatever it actually takes) and let the coco do some real drying out; then turn the system back on again for say another 2 or 3 days (then off again)?