It all depends on what type of plants you have and what kind of lighting you give them. You should look up the light needs of all the plants you want to grow. If your pond is completely indoors now I would focus on low to medium light plants only.
The general guideline commonly used in propagation for fluorescent bulbs is 4-6 inches above the top of the plant. As the plants grow you will need to raise the lights so the bulbs don't burn the meristems.