[Delphinus]

I'll share my own experiences and the reasoning for asking what others do.

I run a tiny little ball of chaeto in an aquaclear lit by 2x9w PC's. This is for a 115g cube so it probably really has a negligible effect on NO3/PO4 pulldown.

I've never been able to get a reading higher than the lowest category on a chemical based test kit. So for some this means "zero" and while others like the D-D/Merck it means "0 to 0.008" (which may as well be zero).

Don't have a lick of GHA in the display, although sometimes I will find some growing in the overflow eggcrate.

Most SPS I have exhibit very poor growth rates (or abnormal mortality rates). I was initially convinced this was due to phosphate but never having been able to establish a significant nonzero reading on any testkit (including the $300 Hanna colorimeter), I started reaching out to other explanations, including pathogens. The story of the last year though is that I am now starting to believe it's not pathogenic in nature ... so I'm coming home to the phosphate theory.

If I could establish that there is a difference made then I would gladly revert back to using GFO. And yet, when I ran GFO in the past, it never made a difference; nor did my brief (6 month) experiment with Zeo.

But so far it sounds like that for those who have noticed a difference with and without GFO, that the difference was enough to be profound, or at least, enough to actually notice a difference. So this is still confusing to me as to whether I may truly have a phosphate buildup or not.

Anyhow thanks all for the comments and thoughts. It is all very interesting to me.