What is causing this hair algae!?!?!?

I setup up this 10g divided dirted planted betta tank a couple months ago and I'm now struggling with hair algae. What is causing it and how can I fix it? I know I can manually remove it but that won't solve what's causing it.

Light
20" finnex stingray

CO2
DIY citric acid/baking soda mix

Plants
Ludwigia arcuata
pearlweed
rotala 'green'
crypt balanse
crypt wendtii
java moss
java fern 'windelov'
dwarf sag
hydrocotyle tripartia