I ordered two hydroponics kits; both of them came with gro rocks. I was curious to know if I could use the Mini GRODAN Grow-Cubes instead of the gro rocks? I'm afraid since they would be constantly wet without drain that the roots would not survive.

In most cases you can quite easily use the Mini GRODAN Grow-Cubes instead of gro rocks. The only time I would not recommend it is if the Grow-Cubes were completely submerged in water 100% of the time. That situation is not really suitable for any other plants that swamp-plants (even with gro rocks).

I am guessing that your kit must be some sort of ebb and flod system… Normally the pots in these types of systems have holes in the bottom. Primarily so water can get in and out.

With regards to gro rocks, you would be required to water continuously. Using GRODAN Grow-Cubes you can do the same as if you are growing a water hungry plant. However, you must stop watering about 2 hours before the sun goes down. This allows the cubes to be drier at night. Remember the plant does not grow in the dark; no light, no water.

I would highly recommend that a timer is attached to the system when using GRODAN and that you only run 1-3 water cycles per day.