Best Medium For 'Straight To Drain' Grow

I am in the process of updating my converted closet size grow with running water and drain. I'd like to be able to mix up a 5 gallon bucket of nutrients and have it water x number of plants in 1 or 2 gallon pots every other day. The excess would flow through to drain. I am growing with dirt now and the drain will come in handy instead of hauling plants to the sink and dealing with a mess. I'd like a similar set up minus the dirt. I read one thread were someone was doing something similar with rockwool (rockwool can be bought outside of cubes?) and capped with hydroton, but I am sure there are a million other options.

The companion question that I should have asked would be what the recommendations would be for nutrients. I have a bottle of Ionic Grow 3-1-5. I had bought as an all around grow formula for a continuous flow/reservoir hydro set up. Would the nutrients change for 'straight to drain'?

Bump - anyone?

coco
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I always use 4x4 rockwool cubes, then put the whole cube into hydroton pellets.