Phosphate/GAC Filter 100gpd The resin color changes from

The resin color changes from blue to a light brown/amber color when it is exhausting

For use with standard 4

The sponge should be moist (not dripping wet)

Not quite what you were looking for

Phosphate/GAC Filter 100gpd The resin color changes fromPhosphate GAC Filter Phosphate GAC Filter By Aries Aries FilterWorks Carbon Phosphate combination cartridges use carbon to effectively improve taste and odor by removing chlorine and phosphate to reduce scale buildup. This combination of Premium GAC carbon and phosphate dramatically improves the quality of drinking water, as well as its ability to protect metal parts from corrosion when used in certain industries. Dimensions and Weight Dimension: 10"