This is why I stopped GFO and started dosing lanthium. Results have been amazing, and I can directly drop my phosphates .03 at a time per dose. Zero impact to SPS, while GFO nearly killed them. I also have 3 tangs that I've noticed zero impact from dosing as well. I simply shoot 1ml directly in front of the skimmer, no drip needed for my 93g tank.I would add to that list that some folks, including me, have noticed recurrent tissue striping in SPS when running GFO.