Two things I think were major contributors to less frequent water changes - 1: Tropic Marin BioActif reefsalt, and 2: Midwest Aquatics Sulphur Denitrator. Both of these together have really made an impact on how my tank processes waste. I also recently added a Kalk stirrer, and use Brightwell Kalk+ to keep up on the trace elements. so instead of turning up the CA reactor and dumping more CO2, I now add kalk to make up the difference. Has really worked for me...