Well my scrubber has bee my sole filtration for years now and I almost never change any water,however I have been having some small issues with the tank this year such as a lack of coraline and some bleaching sps corals. well I went to a good LFS who used new seachem test kits and here are the results:

ph=8.3

alk=10

ca=600

mag=1500

amm=o

trate=o

phosphate=2 not .2

strontium=7

iron=

I have a few questions.

1. I dose Iron all the time,how can it be zero?
2. My strontium is low,should I dose it? does coraline or turf algae use this?
3. Why is my scrubber not removing any phosphate?