a tall 56 would be a great tank for angels , koi angels get tall and when they get large will eat small fish , interesting to watch . tank mates should obviously larger so as not to get eaten . rummynose tetras would be a good schooling fish to go with them .
how about a nice school of cory cats , preferably 6 or more of the same species . then an addition of a smaller pleco like the L18 gold nugget . it should make for an interesting tank and something for everyone .
the hard part about stocking a tank slowly is making a planned stock and sticking to it .