Ya I cured the rock for months but didn’t give a muratic bath. Everything was great for like a yr and this last 8 mths or so been a bit of a battle. Been useing phosphate E which works real well to lower po4 but I don’t like doseing it all the time. Looking for more of a natural removal of the phosphate.
Several people on my other forum have been using RowaPhos. I know it’s not natural like you were looking for but apparently a little bit goes a long way. I’ve never used it myself though.
If they're consistently at 0 then that may be why phosphate is building up, nitrate your limiting nutrient. If this is the case I would try dosing nitrate (in the form of sodium nitrate, potassium nitrate can lead to a buildup of potassium in the system) and see if you can get the phosphates down.
Several people on my other forum have been using RowaPhos. I know it’s not natural like you were looking for but apparently a little bit goes a long way. I’ve never used it myself though.