I have a 20G tank and my issue with algae

So as the title says, I have this 20g tank that always has this algae issue.

I tried filling it up with plants mostly stem ones (10-15 varieties) they indeed grow fast but when they are cut or reaches full bloom, the algae takes over. Then there goes the the molds which covers the lower parts of my aquasoil.

Initial problem is that my tank is being hit by sunlight. Algae was too much so I stopped using my lights and depended mostly on sunlight since its a partly outside tank. But it always gets overun by algae that it kills my stem plants and ends up dying or rotting roots.

Any suggestion for fighting algae or maintaining a sunlight hit aquarium is greatly appreciated.