Welcome.
Not enough info. Size and shape of the things (dots, dashes, fat, skinny)? It can also help to buy yourself a magnifying glass to look in the tank with. Are these things on surfaces or in the water column? Are they moving in the current or actually on their own? If on their own, how are they moving (slow, fast, crawling, wriggling, etc.)?
How long has the tank been set up? Size and filtration? What fish are in the tank?