I am a teacher setting up a 50 gal. horizontal vivarium for my classroom. It has a large water feature that empties into a little pond. It has lots of land for the pdfs and will be live-planted to the max (but there is only 12 or so vertical inches).

I am looking for something on the quieter side, bold, with bright coloring and would prefer something that eats springtails and fruit flies.

I was thinking thumbnails (R. imitator or R. ventrimaculata) but have considered B. auratus and even going the mantella route. I have been doing my research but no one really put a spreadsheet together to help make this decision easy.

Your thoughts?