I do not know if they really are B. opercularis or another Biotoecus species but they do look like it. They are just around 3 cm right now so they have some growing to do. They were listed as wild fish, but they did accept dry food relatively fast. I keep them in an aquarium with the values of 5.0-5.5 pH, 26 Celcius, pretty much 0 gH and around 50 microSiemens conductivity. I just use R/O or distilled water for changes and add a bag of peat to the aquarium every two months or so (and remove the old bag).