Hello,
Many of these guys floating on top of water after watering many potted plants. I am thinking they are springtails. Took this pictures under a dissection microscope. Can they do any harm to my plants? Should I try to get rid of them or let them be?
These are indeed springtails, and ones like these are for the most part harmless detrivores, scavenging bits of decomposing organic matter. Occasionally, they have been reported to cause limited damage to very tender seedlings - see http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74136.html
However, some springtails in the family Sminthuridae (globular springtails) can be quite damaging - https://en.wikipedia.org/wiki/Sminthurus_viridis
