As far as aquarium algae go, this one is a perfectly normal and healthy algae that will be beneficial for your aquarium as long as it is not allowed to overgrow. It is also known as hair, thread or green spot algae (GSA).
This green aquarium algae usually adheres strongly to the surface of the aquarium walls and other hard surfaces like rocks or wood.
If you see green spot algae on your plants, its likely due to low phosphates. If you spot it on the glass and not the plants, then you can easily get rid of it by scraping the surface.
Excess light, excess nutrients plant.
Do regular water changes, clean your aquarium more often, avoid overfeeding the fish.
How to remove
Scrape off the affected surfaces (glas, wood, rocks etc.). Increase the phosphate dosing a bit.