Welcome! Algae Bloom most likely caused from your tank cycling. For combating in a cycling tank you need to change enough water to keep the ammonia etc. close to zero. Too much light or too long of a photoperiod combined with a cycling tank is also a cause. This is one of these things you have to wait it out. UV Sterilizer will also take care of it. But root cause needs to be addressed.
Hope you get in under control soon. Good luck with your new planted tank.