How to care for water-rooted bamboo?

I adopted a bamboo plant that came in a very small pot filled with beads and water. I want it to get bigger, so recently I transplanted it to a bigger container of beads and water. The growth of this thing seems to be really slow, so I’m wondering what I can do to make the plant flourish.

For example, would it be okay to add some diluted plant food to the water? What nutrients would make the bamboo really happy?