Ever since I have been keeping a planted tank, about 20 years, it has been the consensus that the substrate should be at least 1.5 to 2 inches in depth. I have not seen anything to convince me that that is bad advice. But, has anyone done enough experimenting, either on purpose or accidental, to find out what happens when you don't have sufficient substrate depth? What is the effect on the plants? When troubleshooting, what symptoms go with inadequate substrate depth? This is for rooted stem plants, primarily, but rooted plants in general too.