Responding to your questions in this thread.
I use oak leaves, they work very well. Maple should be OK. Magnolia I would avoid, I've no scientific data but as I have a magnolia tree |I would not put those leaves in an aquarium. Oak and maple must be completely dried, preferably picked off the ground not live off the tree, and then laid out to totally dry.
The habitat info on the linked site is bang on; I know Matt who manages that site.
I would not use petrified wood, it has been known to affect water chemistry. Real wood (bogwood, driftwood) is fine. Rocks I would also ignore, if you want an authentic habitat.
Other Amazonian plants are any of the Echinodorus (sword) species, and in a 20g two that are ideal are both in our profiles, the Pygmy chain sword
and the Dwarf Sword
. Click on the shaded name and check them out.
On tankmates, definitely have other fish. All apistos can be very shy on their own, and may stay hidden. With dither fish as we call them, they will be out and about more often. And any of the peaceful, quiet characins (some tetra species, hatchetfish, pencilfish) work very well. Nothing active, as this can unsettle the quiet dwarf cichlids. There are many options, have a look through our characins section in the profiles. If you find some you like, and have further questions, ask away. I have kept almost all of those species at some point.