From my experience, the best way would be to divide the tank in 6 separate compartments 1 hait in each compartment, with a cave in each, where each one can disappear and feel safe, until they choose a partner.
Haits tend to bloat when they feel intimidated, if they feel secure and unstressed they survive.
When I first tried Haits I tried 12 in a 150 gal. All died.
The next time, I tried 6 in a 125, 5 died.
Beside a totally stressfree environment as far as aggression goes, warm temps are needed. In nature they live in temps in the high 80s and low 90s F, look up the article "Oh Island in the Sun, The Dominican Republic" by Alf Stalsberg on cichlidae.com, or Breeding Cichlasoma Haitiensus from an old Tropical Fish Hobbyist mag where the compartment idea cam from, sorry I can't remember the year.
Pics below are my pair that successfully spawned many times, following the above advice.