wouldn't straight water and miralce gro be sufficant
 

If soil bound plants have the same needs as hydroponic plants...wouldn't straight water and miralce gro be sufficant to use in a small ebb and flow system, considering some of the solution would stay in the rockwool/grorocks after "flooding"?

p.s I am talking house plants, not organic.

Totally different ways of growing. With dirt you have a buffer between the plant and the fertilizer. A different chemical reaction with hydro than with dirt. That's why it's takes longer to kill a plant in dirt than hydro. With hydroponics you don't have that buffer so you see results immediately, good and bad.

You can use miracle-gro if you add what's missing. Calcium Nitrate and Magnesium Sulfate.