You didn't mention water changes but I would suggest around a third monthly (I like 5% to 10% weekly).
Over the decades I've seen a wide range of ratios in my systems. What I aim for is PO4 between .03 mg/l and .3 mg/l. For nitrate below 5 mg/l. GFO works well to remove excess PO4, wherevr you decide that number is for your system.
FWIW
.03 mg/l is the threshold level to prevent phosphorus limitation in corals, identified by researchers at Southampton University in England using corals maintained in an aquarium for about a decade. .3 mg/l is what corals are subjected to with upwelling in the ocean.
.5 mg/l is acceptable as acros have been shown to incease growth up to this level.
.9mg/l is the level teh Steinhart Aqaurium's ex situ sexually reproduced acro colonies are being grwon out with. Rich Ross's (who's part of the team at Steinhart) has his acro dominate mixed reef sitting at 1.8 mg/l, his tank can be seen at the beginning of his
MACNA presentation on phosphate.
I'm fine if I don't have any detectable nitrate. Corals have simbiotic cyanobacteria, diazotrophs, that can provide nitrates. Corals much prefer the dissolved organic forms of nitrogen in amino acids and urea and the dissolved inorganic ammonia.
Fig. 3 from this paper
Context Dependant Effects of Nutrient Loading on the Coral-Algal Mutualism
And to add to the complexity of the picture, depending on how corals are feeding and the food webs in reef ecosystems, corals might be the source of PO4 (aka DIP, Dissolved Inorganic Phosphorus) in an aquarium.
