Well, mustn't use "plantguru" as my colleague Tom Barr uses that (though he is not on this forum as far as I know).
To the issue. First question Amanda, by "natural" are you thinking true biotope (using plants and materials that would naturally be found in the puffer habitats) or just a "natural" aquascape meaning plants, wood, rock? I'll respond as if it is a true biotope; if it is just "natural" then plant substitutions could be made with plants from other areas than SE Asia.
Dwarf Puffers come from India and Sri Lanka. The substrate of the habitat streams is sand, small gravel, pebbles, iron clay (laterite). So a substrate in the aquarium of brick-red colour (the dull darker brownish-red, not bright red) meant to suggest iron clay can be used, in a sand or fine gravel but dark not light if you can't find dull red. Seachem's Flourite plant substrate comes in a reddish colour, ideal for this setup. This is one setup where a thin layer of laterite under the sand/gravel would be useful, as the plants from this region all need iron; but not
if you use an enriched substrate like Flourite, it would be too much iron.
Pebbles, bits of rock arranged as small caves (puffers establish territories and needing lots of hiding spots) and bits of bogwood also arranged to provide crevices for hiding spots would be appropriate and necessary. Bits of broken clay flowerpots would provide caves and also add to the reddish theme. The stream bed in this area is often reddish from the iron over which the water flows.
And then lots of plants, thick vegetation both to represent the habitat and provide more cover for the fish; a thick planting breaks up the line of sight for the fish's territories.
In a 10g, Aponogetons are rather large. I have A. crispus and A. undulatus in my 70g and they have leaves more than 2 feet in length laying across the surface. One of either species would be sufficient if you do use an Aponogeton, I would think Aponogeton undulatus the better choice, have a look at the profile, also A. crispus is included in the profiles too so you can compare. The A. undulatus in my 33g has remained smaller.
Crypts are ideally suited to this habitat. Several naturally occur in India and/or Sri Lanka, as noted in our profiles. Some have reddish leaves to contrast nicely with the darker green varieties.
Java Fern attached to some of the wood or rock would be good; and Java Moss on the wood or rock also. For floating plants, aside from the Aponogeton leaves, Ceratopteris cornuta or duckweed are authentic.
The lotus plants are strictly speaking not Asian, though many of us use them in Asian aquascapes; the aquarium species of Nymphaea are African, the plants in Asia are a different genus and not common. Still, the red tiger lotus would be a nice touch, and provide more floating leaves (wouldn't need the Ceratopteris with this and Aponogeton).
All of the above plant suggestions manage very well with moderate (lower) light, a good idea with puffers to reduce their shyness. I would not go for more than 3 Puffers in a 10g; males can be quite feisty.
Hope this is of some help. I'm thinking of getting a 5g for my lone dwarf puffer, he arrived with the pygmy corys so was not intentional, but as he eats every snail in the tank
I want to isolate him.