Question - What is a good small fish to keep the nitrogen cycle going? - above... just planing for the future tanks... I was thinking like ghost shrimp... or maybe even a few small tetra's or guppy's... maybe even a Betta? Once I get my 55g I want to get rid of a few of my smaller tank... i.e. move my male Betta to a 10g tank, and get rid of my 2.5g tank... MAYBE!!!