The two levers that actually work are light and food, and both are free. Put the light on a timer at something like six to eight hours a day, and feed less than you think: shrimp eat astonishingly little and uneaten food is what fuels the growth you are scraping off.
Add fast-growing floating plants to compete for nutrients, keep up small regular water changes, and pull hair algae out by hand. That is the whole toolkit.