To me, that tiny bit of green algae in your tank is a sign of a healthy environment, and makes a tank look more natural.
Algae helps control nitrate, in order to be completely devoid of algae, a tank would need to have a jungle of plants that out compete the algae for nitrates.
Or more frequent water changes would need to be done, not 75% each time, but many more than once per week to reduce nitrate to almost 0ppm.
I doubt your shrimp will last long enough to make a dent.
Cenote Cristallino below, has very light colored rocks where algae is constantly grazed on by mollies, and yet still lots of algae.