Until you see a 18-20" male in a 180 you won't understand how even a 180 will be cramped. I'd suggest a 240g min for a male and 350+ for a pair. And even then that won't guarantee you that the male won't kill the female which is common after a couple of spawns. Understand that taking on a male dovii is a huge commitment of time and finances. Goodluck
ive seen a 18" male dovii before, it was in a 180 if im not mistaken, but i was wondering peoples opinions on keeping them in one (he had a girl friend to).