That is one species of brush/beard algae. It is caused by nutrients and light. In a planted tank, it occurs because these two factors are not in balance for the needs of the plants. It may be too much (bright) light or too long a duration, or too little, or too much nutrients or not enough. In other words, any aspect of the light/nutrient imbalance can cause it.
Knowing the light data--type, watts, spectrum, duration--and what if any fertilizer is being added will help diagnose the issue. Without resolving the cause, no temporary cure will be of any value as it will just come back. I have battled this particular algae a few times, it can be beaten.