According to Anthony Calfo and Robert Fenner, you should not have shrimp in your refuge as it will keep the fuge from working correctly, the shrimp will eat on the macro algae you have and other beneficial life forms. They say Crabs are the worst animals you can have in you refugium. What you need to figure out first is the function the refuge is going to do as there are many. Also it is never really a good idea to mix algae in the same refugium as it will compete with each other and can cause water quality issues, it is best to pick one kind of algae and use that one. Cheato is the best as other caulerpa algae species can die and hurt your tank. You can also use live animals such as xenia, feather dusters and much more.
This is what I have, a 100 gallon tub of Cheato, I split my sump and have a mangrove tree (soon to add more) and some other algae growing there, it is not yet finished. I am also adding sponges and sea squirts to the 300 in protected areas, these two are mainly for the fact that I have no skimmer but would help in any refugium. I also have may xenia type corals starting to grow in the 300.