This usually happen to new tank if too much nutrients is added too quickly into the water which good bacteria has no time to populate. We usually have algaes for new tank but it cannot take over the whole tank. Is it taking over the tank? I will suggest reduce lighting n nutrients. Any livestock in it? And do water change more frequently. Hard work but effiective in reducing no3 to give time for the tank to get stable. Buying algae eaters temporary solve the problem but if the problem is that the tank is still not stable then algae eaters will not help in the long run. You can dose bateria whenever water change too to increase the rate for good bacterias populate. Sent from my SM-N915G using Tapatalk