Tested the solution last night after the GFO had been in the second batch for about 24 hours. Did exactly as before...stirred the GFO, took out some of the lye solution and diluted with RODI 100:1. Tested phosphate and got a reading of about 0.5. This had read about 1.0 after 4 hours with the first batch of lye.
The I used some distilled white vinager to get the PH to about 8.0. Took a few tries. This time it read about 1.0ppm phosphate. About double the reading I got with the high, unadjusted PH. I managed to overshoot once and got a PH below the range of my test kit (less than 7.4). From the PH test color I'd say I overshot a lot. That read 3.0 phosphate. I'm assuming the 1.0 is about right.
If the doubling is right, my first batch of lye was at 200ppm phosphate and the second 100. 4 liters each time so 1200mg total removed from the GFO so far. There's about 700 liters in my system. The GFO droped the phosphate from about 1 to close to zero in 4 days. So it took about 700mg that was originally in the water plus at least 500mg more that must have leached out of the rock or come from food. I fed the tank about 20g of Rod's H total over the 4 days (5 grams each day).
The tank reads about 0.5ppm phosphate this morning. Up from 0.05 to 0.5 in less than 48 hours, about 350mg.
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