The issue is, there is no issue. Your plants are beating out any algae for nutrients.
If you want algae, I'd say run lights for 12 hours and remove some plants but honestly, there is always algae growing in our tanks if it's low tech. It's just so little it's hard to see. Imo, i wouldn't strive for growing algae to feed shrimp. I feed algae wafers, blanched veggies and other shrimp foods. The shrimp will eat up algae and biofilm you don't really see as well.
Throw a larger size stone in a jar of tank water and put it in the sun. Algae will grow. Dont will it in your tank.
As mentioned above, you probably have small amounts of algae, even if you don't see it, but it really doesn't matter. If your tank is at least several months old it will have plenty of biofilm for the shrimp to graze on. They don't necessarily need algae.