Yea I can attest that rockwool does hold onto water very well. I could almost get by watering them once a day with spray bottle becuase they seem to really retain the moisture. But that also leads to my concern about overwatering as well. What I think may have been happing with my previous grows is because I was maybe getting such severe nute lockout that I got all that sediment in the bottom of my resv. and now that they aren't getting locked out they are being overwatered. I don't know if that is logically sound or not?