Its green slime algae. Its actually poisonous to fish snail shrimp. Its actually a cynobacteria and will continue to spread until its all gone.
Turn of the lights for 48hrs or more during this time dont feed or any light in the tank, i put a towel over the glass to assure no outside light gets in.this the cynobacteria should die off. Do a large water change and suck out all the dead cynobacteria if its not all dead extend the black out up to a week. The fish will be ok not eating for a week the plants wont like the dark but they dont like slime algae either and as long as their roots are intact theyll be fine. After blackout do large water change, remove any leaves that look infected.good luck slime algae is the worst. Also invest in some anacharis plant, it is said to have something in it that wards off slime algae in tanks