Miracle Grow for use in hydroponics?

[Mathieu]

I am planning on using a product, Miracle-gro, that has all the necessary nutrients except for calcium and magnesium. I will add epsom salt and lime to substitute. My question is about the nitrogen in the solution.

It has 15% nitrogen, 8.2% ammoniacal nitrogen and 6.8% urea nitrogen. The oxygen is from ammonium phosphates. can someone please tell me if this is good for tomatoes. I have heard that urea nitrogen is not good for tomatoes. Why?