Nick if your not getting any white film on the glass , corals are healthy you can continue to raise the carbon source , as mindy said as long as there is available po4 the bacteria will use up the available nitrates as well. The good news about being phosphate limited vs nitrate limited is phosphates are easily added via foods.
If you quit e gfo what happens? Do your phosphates go up terribly or do you run it just in case to keep it low? Your po4 test numbers fall pretty close to margin or error.
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