Those two green spheres are bubble algae. If they grow big enough they will pop and produce spores all over your tank.
Best way to get rid of it is take out the rock (if possible) and just pull it off. If you can't take out the rock, you can try pulling it off in the tank. If you do this take your suction hose right by it while you are doing it just in case it pops, then you suck up all the spores.