Well in soil you can use it all the time (in veg). Anywhere from a teaspoon to just a drop per gallon. But IDK about hydro. If you are using another rooting hormone i'd just stick with that rather than trying to use both.
I've never used rockwool. I assume the rockwool cubes are sitting in some amount of water? If you could oxygenate that water....I'm sure that would help. Like I said my clone didn't root till I added the airstone.
I'm still tryin to figure out the message system in this place?
Seems like there's more than one type of message. Some I can retrieve, some get lost somehow?