ok, so first, there's Green Hair Algae - derbesia. Then on top of that, most of the brown pigment is diatoms growing as epiphytes on the GHA. Then there's small zooming cells that are moving in a way that's a little unusual for dinos. Could be dinos, but I think another flagellate or ciliate is more likely, and I dn't think they are a concern. At higher power might be able to say more.