From memory don't they grow in the pools on Trill in the caves?
Yes, there is a scene in Equilibrium in which we see unjoined symbionts in a pool being cared for people called “Guardians.” In this unjoined state, they are conscious, and swim around and communicate with each other through some kind of electrical signals that are visible like lightning.
What the episode does not explain is where those symbionts came from, and I mean that on both the individual and species level. Where does an individual symbiont come from? Are there a mother symbiont and father symbiont that somehow mate and give birth to it? And what about the species? Did it evolve naturally, or was it created?