Yeah, those are cyclops/copepods. Nice pic of these little guys! What did you use?
They are harmless, though I have heard of some carnivorous copepods (small as they are though, I would doubt they cause any noticeable issue).
Most fish will eat them. They are generally only present in a large enough colony if there aren't enough predators to keep their numbers low. Snails and Shrimp won't eat them, or at least make any sort of noticeable decrease in their population, since they are popular in shrimp tanks. Overfeeding increases the cyclops population (good if you use them as live food, bad if you just don't like the site of them).
If you want them gone, just feed less or add more fish to eat them (you can scoop out some copepods too). Not feeding the betta, should have it hungry enough to devour the copepods more.
Water fleas is usually a common name for Daphnia though, bit different from the typical copepods.