I would recommend starting up a shrimp tank and getting a healthy colony going.
While that's working, you can start planting your 20g to have more dense cover (ground plants and moss are great!). Once you have a good colony going in the shrimp tank and good foilage in the 20g, then you can start introducing some shrimp into the 20g. (as long as it hasn't been treated with copper)
While that's working, you can start planting your 20g to have more dense cover (ground plants and moss are great!). Once you have a good colony going in the shrimp tank and good foilage in the 20g, then you can start introducing some shrimp into the 20g. (as long as it hasn't been treated with copper)
