[Big E]

If I remember correctly when people were having trouble with Rowa years ago, it was the alk that was being affected & that what was making the acros RTN.

I don't think it's the phosphate levels that are the measurement you should track. Try watching your alk maybe there's a connection there.

Like I mentioned earlier, you could try dosing vinegar for a few months & see if you can get by reducing phosphate & ridding yourself of the cyano.

Or maybe look at your nutrient control methods to control the cyano & phosphates.

What are your methods right now? I've run .03 phospates for years on just water changes, barebottom tank & a skimmer. No chemical filtration what so ever.

At the place I'm living at now the water supply has been different & I had some isssues so I started dosing vinegar. I've never used GFO except for on a couple of occasions short term in over 10 years of keeping Sps.