Its a type of hair algae or brush algae. Algae is always a sign of an imbalance in the tank between light and nutrients. Try decreasing amount of time light is on. Algae needs 8 straight hours of light any light to grow. This includes any outside light including indirect window light, over head room lights, even tv light is light algae can use. I put a towel over the front of my tank when tank light are off to keep all light out. Next is intensity of light if light is too intense algae will grow if too low algae will grow. Plants can only take up so many nutrients the light is the engine that allows nutrient absorption, if light is not sufficient algae will use nutrients, if light is to bright plants will use what nutrients they can and algae the rest. One way to combat this is by adding more plants or decreasing nutrients through decreased feeding and regular large water changes. In case of too low light simply increase brightness of light.
Cleaning filter can also decrease excess nutrients and waste that lead to algae.
Lastly if the problem is lack of nutrients plants will suffer algae will not. Plants need 17 nutrients to grow, if one is defficient in one of those nutrients plants wont thrive algae will. Algae doesnt need 17 nutrients to thrive it can utilize 1. So make sure plants are getting nutrients they need through water column and roots. Lastly water flow is important not just for stirring up and moving waste but also transporting oxygen and nutrients to plants.
So decrease or increase light depending on where you are at.
Decreasing feeding decrease available waste for algae.
Increasing water changes never hurt
Adding more plants can help.
Good luck.