Algae is normal and natural.. depending on your water perameters you may try doing more water changes, ime algae tends to build up in either high light areas or high nutrient water ( ie high nitrates) Otherwise it's safe and harmless and can even be helpfull to your tank, personally I only algae scrape the front of my tanks that get it and leave the sides and back to grow as they please. You may also try adding pothos to your filter the plant will often out compete algae for nutrients. and manually removing any algae you do scrape off is ideal mainly so it doesn't stuff up your filter.