DIY Shrimp trap.
Cut the top 1/4 off of a soda bottle. Invert the top piece and place into the bottom creating funnel. Presto! Instant trap in under a buck. Free even if you have friends that drink soda.
Fill with tank water and place at the bottom of the tank. Drop in an algae wafer and wait.
Since you have a 55g, you could easily make a few of these.