They're an interesting bunch of fish. They come in varying sizes, depending on origin and which line they are. There is a "dwarf red gularis" in circulation. It gets to 3-4 inches/9/10 cm. After that, they can range up to 6 inches/15cm, although I once saw some very old wild caughts come in that were larger than that, and murderously aggressive. They were past breeding age, but really impressive beasts.
They are semi-annuals, with eggs incubating in peat for weeks to months depending. That makes buying eggs easy, on Aquabid or through killie clubs. But variability hits again - some lines will hatch in water in with the parents, and some need incubation on peat. They are in an area threatened by a combination of the oil industry and human population displacement and growth, and I don't know of anyone studying them. I expect that if someone sampled wilds, they might find more than one species under the name. Most of the ones in captivity are mixes of different catching location, often going back several decades.