It's a good idea to learn as much about your tank, in order to give it the best care. Knowing what kinds of fish you have is quite important.
As for the anemones, they are most likely, Aiptasia. They are a pest anemone that can sting corals. Do you have corals? If not, do you plan to in the future? If both answers are "No," the aiptasia aren't really a concern. If either answer is "yes," you need to learn how to deal with aiptasia. There are many remedies that have varying degrees of success, from chemical treatments, such as Kalk paste, Joe's Juice, boiling water or Aiptasia X, to biological controls, such as Berghia Nudibranchs, Copper Banded Butterfly fish and Peppermint Shrimp.