By Robalex
Oklahoma,
United States 
I try to grow radishes indoors with T-8 grow lights just about 2 inches above, use Miracle-Gro, and water well.
They always have good leaves but leggy stems and no bulb.
17 Dec, 2015
Answers
possibly you are over feeding them. this will produce lots of leaves. the bulb part is the plants strategy to 'overwinter' so it can flower next year, if it isn't getting the signals to bulk up it wont. So try reducing the feed and see if that makes a difference.
the light should be the correct wavelengths if its a bulb designed for growing plants. its not an aquarium light is it? the wavelengths for them is slightly different as aquatic plants have additional photosynthetic pigments in them.
18 Dec, 2015
T8 fluorescents or T8 LEDs, Robalex? What color balance--i.e. actual "grow lights", or "soft white"?
19 Dec, 2015
Leggy stems suggests not enough light.
17 Dec, 2015