Oh wow! I think I am going to use PHOS - E just to have a bit more controllability and not drop to fast. @DaddyFish recommended this over Phos-RX, although not sure why.I used phosphate RX when I had 0.90 po4 and dropped it to 0.10 in 3 days
Still would love to hear some more opinions on Phos-E vs Phos RX