Welcome to AA!
The tiny bugs you are seeing are most likely pods
... tiny shrimp-like crustaceans.
As for your tank, I would suggest researching any new fish you want before you buy them. A 40 gallon tank is too small for a tang of any kind, much less two of them. Damsels tend to be very aggressive and territorial and many hobbiests end up removing them from their tanks. Clownfish are good fish, although some species can be more aggressive than others. They can be kept singly or in a pair, but don't mix different species in the same tank.
What are the levels in your tank right now? (Salinity, PH
, Ammonia, Nitrite, Nitrate)