They are most likely copepods. These are tiny crustaceans which feed on algae and other detritus in your tank. They can also serve as a food source for many fish. Look for their cousins, the amphipods down in your substrate. They are the little "comma-looking" bugs which are a little bigger. Both are a sign of a healthy ecosystem and you don't need to do anything about them. Just sit back and enjoy! If you feel they are starting to take over, you can get a fish that specifically eats them like a mandarin goby, but you should never have to really worry about this.