I was thinking of something similar to a South American biotope. But I have limited choices because of my discus and I don't want any other cichlid in the tank besides him. He has to be the star. I forgot about otocinclus, thank you for reminding me, definitely have to add some.If you have soft acidic water PLEASE South American Biotope. Those tanks are gorgeous and so interesting! And in a 90G??? Man, you could have an amazing setup... You could have angels, with fuller-bodied tetras, or smaller tetras with SA dwarf cichlids, Corydoras, Otocinclus. It's one of my favourite tank setups.