I've actually raised two convict from 3-5 week old fry to 3/4" & 1.5" in that 55 with the current stock without issue...leads me to believe I have a pretty well behaved group of fish. But you never can tell.
yes but con babies are notorious, for getting away, hiding and surviving..so no surprise there , that is why some people don't use them as feeders, bettas on the other hand are no where near as fast, or aggressive...i would go with the 20 and give him a dream home ^_^
