Simpsonichythys constanciae, aka the Featherfin Pearlfish. Recently re-classified Simpsonichthys constanciae (frmr. Ophalmolebias constanciae) São João basin from Brazil. This is an IUCN vulnerable annual species. Two males in ritual display combat for the attentions of four females in a heavily planted 40 gallon tank they share with a colony of clown plecos. Switch spawners that love to scatter eggs in peat or moss plants. Whichever male wins this combat will be the dominant breeding male. There is sufficient territory and line of sight breaks in the tank for the sub-dominant male to retreat to.
I love it when I see rare fish in my care displaying mating behaviors. I feel blessed. Please ask questions or comment below. Enjoy!