I say a planted Dwarf Cichlid tank!!!!!!!!!!!!!!!!!!!!!!!!!
2 Cockatoo's
2 Kribs
2 Blue Rams
6 Coconut Caves
4 Amazon Sword Plants
10 camboba
a few grass type plants
and a few moss balls
That is pushing it, but you could try to fit in a school of tetra's
i was thinking of a south american black water with lots of bog wood, 1 or 2 amazon swords, 1 or 2 vallis, 2 bolivian rams, 2-3 apistos or keyholes, and 6-10 rummy noses
never heard of buying blackwater "stuff" all you need in lots of tannis, that makes the water soft, and basicly creates a blackwater replica (from what i remember)
Personly Id go heavily planted and depending on dimensions, maybe some angels, few shoals of various dither fish (tetra, rasbora etc) and maybe a pair of BN's/Bull Dog/Pit bull plecs.