Does my tank look okay?

your pure ro/di water should be 0, do you have your own ro/di unit or are you buying it from a machine? phos will keep building up unless you have a way to remove it. any livstock will contribute to the phos level it could also be leaching from the rock.

 

phosphates enter the aquarium from fish and invertebrate waste and decaying organic matter, such as dead algea and uneaten fish food. Water treatment facilities may add phosphate to tap water to prevent pipe corrosion and reduce concentrations of heavy metals in drinking water. Some salt mixes also contain phosphates. (REF from API Aquarium Pharmaceuticals)