Plants rooted in 4" rockwool cubes.... Ok for the UC?help please

[Bubba kush]

My plants are about 12-13 inches tall and growing very strong so I transferred the cubes into the under current net pots on top of some hydroton. My question is how high should the water level be. I'm kinda worried about the bottom of the rockwool cubes sitting in the water. Would that cause root rot?

 

[ALLegal420]

Yea, avoid having the rockwool cubes sitting directly in water, I have roughly 1-1/2" of hydroton that my 6" cubes sit on. The water line is roughly 1" up my net pots, that leaves me with a roughly 1/2" gap.

-ALLegal420