Thanks for the reply! I knew there had to be at least one other fish nerd who was willing to experiment with cories in cooler tanks.
Right now its panda loaches, CPDs and stiphodons.
During the winter the tank fluctuates between 65 during the day and 60 at night. Now that its spring the temperature is starting to hold at around the 68-70 mark, and water temps will hold at around 75ish during the summer.
Out of curiosity, have you tried any other amazon species? If cories can handle constant 50-60 degree water, it only makes sense that many of our common tetras should be able to do the same (I've kinda been eyeing hummingbird tetras)
I'm not keeping anything that actually needs lower temperatures, but I like cooler tanks because 1) I save on the electric bill by not running a heater, and 2) I find cooler temps help with my plants a TON because the water holds on to dissolved gasses better (including co2) and I just get really nice, robust growth that looks like it was grown with co2 injection despite not using co2.
Plus, I like to think that my fish appreciate the boosted oxygen levels.