Hydroponics is the method of growing plants in a nutrient rich solution instead of soil. In hydroponics, plants are grown in this nutrient rich solution with or without the mechanical support of inert or artificial medium (sand, gravel, vermiculite, rockwool, perlite, peatmoss. coir, or sawdust). The roots of the plant are grown in water that has been enriched with mineral nutrients.
There are 13 mineral nutrients:

3 primary macro-nutrients which are Nitrogen (N), Phosphorus (P), Potassium (K).
3 secondary macro-nutrients which are Calcium (Ca), Magnesium (Mg), Sulfur (s).
7 micro-nutrients which are Boron (B), Copper (Cu), Iron (Fe), Chloride (Cl), Manganese (Mn), Molybdenum (Mo) and Zinc (Zn).

If you lucky bamboo has always been in water, I suggest you keep it in water. If you have an over-abundance of roots or unhealthy roots, you can selectively prune them. You might want to read more about Caring For Lucky Bamboo

Lucky bamboo can be planted in water. First gently wash all of the soil from the roots; then fill your container with distilled water about an inch to an inch and a half. The stalks will go through transplant stock. It is important that you don’t fertilize it during this time. Give it a couple of weeks and it should be find.

Kim,

Lucky bamboo doesn’t care whether it has 1, 3, 5 or a bazillion. Only that it has the proper care.

However, different numbers of stalks symbolize different kinds of luck.
2 stalks = love
3 or 6 stalks = happiness
5 or 7 = health
8 = wealth
9 stalks = general good fortune
21 stalks = blessings