I kept freshwater fish my whole childhood. Started with goldfish then the common guppies, tetras, angels etc and from there moved to south american cichlids like Jack dempseys, convicts, fire mouths, jewel fish. They were great but it took such precision in sizing, timing and temperament to keep them together without killing each other. My next progression was going to be african cichlids but then in college (early 90s) one of my best friends was a marine biology major. I got my first bag of crushed coral over an underground filter and a damsel around 1994l and never looked back. It was natural progression for me. The kind of freshwater fish that interest me now would require a minimum 210g.