Add some driftwood even if it means replacing some of the ceramic decor, because they really like snacking on the bio film that grows fastest on wood.
Add some surface plants to keep the tank more walstad-like. One of the biggest unexpected changes for fishkeepers is the difficulty/impossibility of gravel vacuuming the bottom without sucking up all your baby shrimp. I heavily plant shrimp tanks to permit them to stay healthy without frequent cleaning of the floor.
justjokay 
Add some driftwood even if it means replacing some of the ceramic decor, because they really like snacking on the bio film that grows fastest on wood.
Add some surface plants to keep the tank more walstad-like. One of the biggest unexpected changes for fishkeepers is the difficulty/impossibility of gravel vacuuming the bottom without sucking up all your baby shrimp. I heavily plant shrimp tanks to permit them to stay healthy without frequent cleaning of the floor.
Get rid of the plastic crap and replace it with driftwood
add some moss, the shrimp love to hide in it and it’s a great place for beneficial bacteria to grow for your shrimp to eat
Just a heads up beta fish are known to eat shrimp. the only shrimp they seem to leave alone is adult amano shrimp