I have never kept penguin tetras and don't know how they will behave in such a large shoal in an aquarium. I know there is a species of penguin that grows quite large, almost 3 inches, ... I'd keep away from that one, or have just a small number of them. I have kept rosy tetras and BHT, among others, at different moments, in groups of up to 18. This was in a 125G. I also had some 20 cardinals (they were eaten), about 6 medium sized plecos and about 8 wild rams. Like I said this was a 125G I had in my home as display... I really don't have any display tanks for now.
God listens. He may not always give you everything you want, when you want it; but he always gives you what you really need, when you need it most!