Sell a pair or two to me
Unfortunately lowering the temp even to 82 or 80 is not going to shut a pair down for long.
One solution amongst keepers of African Cichlids is to stock only males in a show tank.
So long term for your single show tank keeping only a female tank or a male tank is one of the few surefire ways to prohibit breeding. Having said that I have two female turquoise in a tank that lay every week or two. Need to get one or both of them a boyfriend. To grow them up to biggest size you should separate the sexes.