hello, i am having very good luck with an amazon biotope that was inspired by the same book you are talking about. the tank i have is 150 gallons. it has way too many fish- 1 raphael-that i never see, 13 lemon tetras, 10 glolight tetras, 10 blue tetras, 4 bolivian rams, 5 bristlnosed plecos, and 6 brilliant german turk discus- which are beautiful and healthy, in addition to these I have in quarantine 10 marble hatchetfish. from all these fish that i have kept, and looking at your list if i were setting up the 55 gallon I would do 4 rams, 4 discus, 6 hatchetfish, 6 rummynoses. the reason i dont put in cories is that the rams occupy that space for me and they draw all the attention for me, but what i figured out is they are all fish. i knew from reading that if i tried discus they were for some reason not going to survive quaratine, i had read so much and was so scared i didnt want to try, but then my husband said they are just fish honey, and you know what they are. so i took the plunge, and they have also doubled in size since i got them 6 weeks ago, and are doing great. so i wish you luck, there will be mistakes, but have fun and keep trying and keep us all posted.