I'm use soil less mix with no rocks at all.. No issues around water retention or medium falling out.. From a general standpoint, I use about 2 qts per plant (#2 pot ~ 1 1/2 gallons medium) in the flower room about every 2 1/2 days, give or take depending on strain, etc., and a little more with the larger containers. I've also started leaching (right term?) the plants around week 4 or 5 in flower with a nute solution of about 400 ppm.

I have one plant now that was trying to grow out of the bottom of the pot. My hydro buddy was worried, but they just stopped once they got a bit dry in the light. Plant stayed perfectly healthy..