[Peter Finke]

1. The 30 liter is not overcrowded by 5 Paros. Mind, that s small cave is heaven on earth for a pair of them. In nature, they live in small groups mostly in an space not much bigger than a small tank. Here, all enimies are missing. More space is possible but makes Paro-care more difficult. When the first pair starts breeding, than the three other fish will be forced to a corner, however. This could make the 50 liter a preference.
2. The honey gourami is a fish that will never occur in oligotrophic blackwater streams but in eutrophic ponds and rice fields. It’s a completely unecological combination. And H. amandae? Why that? Mind that Paros are highly endangered fish, and the Parosphromenus Project does not recommend to use them as ornamental inhabitants of nice community tanks. If this is your aim, take south American Nannostomus-species.
3. The Pangios, if they stand the highly demineralized milieu of the blackwater tank, will certainly have the effect that no young will grow up in your tank.
So, you should decide what you want. You did not speak about plants; I am afraid that is a further problem. You said “The tank is blackwater”, but you seem to be not conscious of what that means and what you really want.