Identify what is responsible in your system for the phosphates initially. Are you overfeeding? Do you have fish, perhaps wrasses who burry, and disturb the sand bed? Perhaps a circulation pump turns on at times of the day and completely shifts the sand bed.
These would release phosphate into the water at a rate live rock could not export it. It is my personal opinion that GFO is not a media that needs to be ran constantly. It can be very effective at lowering phosphates in an emergency should you need to. Phosphate is a major nutrient for corals and is needed for growth actually. Yes too much can decrease growth rates and pigments of corals, but surely should not jeopardize your animals lives.
If we're okay with nitrate at 1,000x NSW why do we have such a big area of focus when phosphate begins to creep up slightly? Where did this .02 or .03 number come from?
If you wanted to run media to decrease nutrients, I like bio-pellets because they remove nitrate as well in a specific ratio to phosphate. But this is already a function of live rock. The tumbling effects of bio-pellets increases their ability to export, but none the less a tank with sufficient established live rock will see the same results as bio-pellets.
Should nutrients raise beyond live rocks functionality I would consider larger water changes with focus on removing nutrient in the form of waste in filters and sand bed. I use turkey basters to clean rocks of detritus and like a higher flow. Obviously larger water changes in a 150gal isn't going to do much for testable nutrients but will give more water to remove built up waste. Like in those areas we all know gather it around the rocks and corners.
If I did run a reactor it'd be for carbon.
Nutrients may be a bigger factor to tanks who have bigger fish with higher diets but with detailed sand vacuuming you could still see live rock export the brute of nutrients.
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