Given that this tank will be 24" high, I was wondering about fixing
plants in the rock pile I intend to build at the back. That will get
them nearer the light. The vals could always be planted in the
substrate, in cracks between the rocks where the fish couldn't easily
get to them.

I had and still have this issue in one tank... what I did in the bigger tank
was plant them and put rocks near to the base without crushing or touching
the roots... My pl*co was the culprit though, he's so big, everytime he
turned a corner, up a plant went to the surface.... eventually, putting the
rocks around the base made them stick, and now he doesn't uproot them, he
lays on them.... nice anubia lounge chair....