I took a look at the Seriously Fish entries for both species (
here and
here), as well as the original descriptions of
Betta dimidiata (
here) and
Betta enisae (
here) and it appears that they're both found in the same general area, and occur in the same habitats. In fact, the description of
Betta enisae mentions "it was always associated with but much less abundant than
B. dimidiata."
There are indeed two rivers named the Kapuas in Borneo; they are both in Kalimantan (Indonesian Borneo). The larger
Kapuas River flows westwards through the province of Kalimantan Barat (West Kalimantan) towards the South China Sea; the 2 species of betta you are keeping are native to this river. By the way,
Sanggau Regency is in Kalimantan Barat, making it part of Indonesia, not Malaysia. The other
Kapuas River is much shorter, and flows southwards through the province of Kalimantan Tengah (Central Kalimantan) into the Java Sea.
As for suitable plants and tankmates for your biotope, you can try looking for species of the Danau Sentarum lake system, which is part of the Kapuas catchment of Kalimantan Barat. There's a list of fish species recorded in Danau Sentarum on page 166 of
this document by the Borneo Research Council, but it is likely outdated as it is already 17 years old. Interestingly, no species of
Boraras are listed, although several barbs and rasboras are included. Plants are also listed in that same document, from page 89 onwards.
Hope this helps!
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