As Wildbetta has said, add in more plants! Both Hornwort and Anacharis grow very well in low light to high light conditions and they compete for nutrients with the algae (more often than not, the plants win the nutrients)
Ghost shrimp do nothing for algae, they are specifically scavengers that eat left over food and other various things. But Cherry Shrimp and Amano shrimp are excellent at clearing algae and if you house both of them, it kind of works like an assembly line where the Amano's eat bigger stuff and tear it up to smaller pieces so that the Cherrys can then process it. And best of all, it's a super light bio-load.
But of course this all depends on what you currently have in the tank, which I believe you said some cory cats? But what else is in there and what types of plants do you have at the moment? Oh and the size of the tank which I don't think had been mentioned?
Leopards: 1:4 Hawkeye, Luna, Astrael, Dorian, Cullen