First, you have not proven a practical way to use calcium hydroxide to directly reduce phosphates in our saltwater tank. The theory is there but in practice it would be very localized and in extremely small amounts. Maybe some kind of reactor incorporating calcium hydroxide, hydrochloric acid to handle the alkalinity spike, and very fine filter to handle the precipitate. Maybe some CO2.
Either way I'd like to see your reference to using limewater in a ease and practical way to reduce phosphates that is cheaper and more efficient then GFO.
Second, I would love to also now know how nails will practically work as well. Randy in that link you provided brought up several valid points.
1. Yes, it will rust and convert
2. Contaminants are a concern
3. You would need an extremely large amount of nails to compare to th surface area of GFO
4. Point 3 makes point 2 an even greater concern.
Contaminants would not just come from a surface coating. To make this work you could create maybe a reactor out of a large container filled with nails pumping water through it. That doesn't sound practical or powerful.
Would be easier to dose iron citrate like GlennF does or use GFO. I believe GFO in a small reactor to be safer.