I know thorichthys are very slow growers, I have a group at around an inch long, how should I grow them faster? I want to breed them in order to produce a larger group for myself. They are t.aureus "rio copan".
Clean water, consistent and diverse diet, and more clean water. Some people power feed fish into growth but it can shorten the lifespan if the fish take in too many calories, especially fats, that lead to fatty liver.
The more you do water changes, the faster they will grow.
Many commercial breeders will change 90% of the tanks water per day (especially discus breeders trying to get them to market faster.
I find water changes are "the" most important influence and factor for growth of any cichlid.