On the practical side regarding GFO in my system I noted a 0.01 ppm rise in phosphate to 0.081 after a few weeks using 500g GFO and high reactor flow. So a week ago I swapped in 250g fresh GFO. Two readings a couple of days apart of 0.054 ppm since. Not optimistic that it will stay at exactly that, but a nice number for sps. Wonder long term about tuning the level using something like a Kamoer continuous flow dosing pump at much lower flows.