Lets see the systems.If SPS requires nutrients explain why I have tanks with *zero* live stock in them, zero nitrate / zero phosphate / zero anything else and acropora are thriving? Explain my friends running large propagation tanks and have *zero* live stock in them with zero nutrient levels and have glorious SPS growth?
Captive tanks are not the ocean. What happens in a captive tank where you have fish and hence dumping nutrients in the water is you have multiple competiting biologies in play all of which would be in check in the ocean with very low nutrient levels. However, in a captive tank with fish those bacteria and algae colonies suddenly have 1000x the nutrient levels to feed on, they pull other nutrients out of the water that SPS require, and start turning on their bio combat engines. Now your SPS are looking bad and we're blaming the low N03 / P04 levels as the culprit. The low N03 / P04 are just the symptom.
This is why one guy has high N03 / P04 levels and no issues while another has zero N03 / P04 and is tank has nuisance algae an inch deep.
I recently pulled two birdnests colonies out of my high nutrient softie garden that had stopped growing. They were perfectly healthy with good PE, but their growth nodes had disappeared over the past month. I put them in a spanking fresh tank with no inhabitants other than other Acros and some Acans, and within 48 hours I saw growth nodes returning and are now back on full blast growth. N03 / P04 are not the issue. It's what also eating those nutrients along with other nutrients and competing with SPS.
Also, we need to stop granting other LPS like euphyllia a not guilty verdict because we think it looks cool. Got a basketball sized hammer coral in your tank that's growing like crazy while your SPS have dying tips and looking weak? Connect the dots.