Question: do shrimp need a filter?
Answer: No they do not, IF you can keep up with water changes often to make up for it. I believe it was TheresaM that threw together an amazing fish bowl and has 1-2RCS in it. No heater or filter. I also have an unfiltered 10g with a large RCS colony; 3 smaller tanks running sponge filters with other types of shrimp.