Welcome to the community and we have some great keepers here to help.
Have you considered Phosguard and Chemi-pure ("Multi-purpose chemical filter media removes dissolved organics and other harmful compounds) " type additions.
Also what are you feeding and what type of stocking?
I am pretty new still with
SW and most of my experience is with small tanks. Others will be able to recommend things and maybe a piece of equipment to help.
__________________