Despite some seeming evidence, I am skeptical about low P04 linked to STN and RTN of SPS. I think it is more the rapid change in parameters especially KH that SPS don't like.
I say this, because my SPS grew fastest (and I mean really fast) and had the best colour when my P04 and N03 were the lowest. When I say low, my P04 usually measured zero with my Hanna checker (only occasionally up to .02 to .04). Then last spring due to some issues (mistakes) it went up to 0.10 and my N03 to 30 ppm. My SPS then lost some colour and growth drastically slowed. But then in the summer I had another problem where my KH dropped to 5 (doser plugged), and that was a fatal blow to some of my SPS. It started with some STN and burnt tips on my SPS, and turned to full out RTN on some others. This continued for a while even after correcting my KH and bringing my P04 and N03 back down. But the good news now, a few months later, everything is turning good again, with SPS colour and growth returning. Even with some of my badly injured SPS (which I had cut off the dead parts) I have signs of life and new growth again.
So I think the big thing with SPS is they don't like change. And once they become unhappy, it takes them a while to recover. Get your parameters in check, and keep them stable, and with a bit of time, things should recover. But if you keep tinkering and changing things, you may continue to have problems. Anyway, that's my theory,... FWIW.
|