Here's some photos I took of my Betta coccina tank. It has a huge semi-decomposing leaf litter of Oak, Alder and Ketapang leaves, and there is a layer of peat mulm and chopped up Ketapang leaves over ADA Sarawak sand for the substrate. Since they inhabit very acidic water (from pH 4.0-6.0) I leave the leaf litter in and just top it up with newer stuff from time to time.
It's a great tank for upkeep. Whatever algae grows looks natural, and when the light is on, the tannin stained water looks amazing. My fish all seem content even if it is smaller than what I originally planned. Having the leaf litter made a massive difference to aggression levels as opposed to just plants. The temperature is also lower than in my Betta splenden tanks, sitting around 23-24 degrees celcius.
The little fish at the very front of the shot is my runt. I can't tell if it's male or female, but it doesn't seem to have grown much since I got it.
They've only striped/clamped up in the photos because they hate when I turn on the overhead light.
Personally I love the coccina complex, and am only sad a soon to be passed law will essentially ban further importation of them (along with domesticated splendens) to Australia