K, maybe I should address it this way. And if it doesn't help you out it's the best I got.
If I have a coral for poor polyp extension I would look to...
- inappropriate or insufficient waterflow
- excessive illumination
- predatation
- allelopathy
- agitation
But there are many many other reason. Of course, O2 has something to do with it... nothing thrives in low O2 environment... a non thriving coral would have poor polyp extension. O2 ties in with REDOX which ties in with coral heath.
