First, thanks for all the help.The question is how fast is the macro algae growing. If the mass is not increasing, nitrate level will not decrease. If you are harvesting the algae like mad, there is not enough macro algae.
There is another possibility. If the macro algae has grown well and stopped even with plenty of phosphate and nitrate, that might be a sign the algae has stripped the water of micro nutrients. This might account for the coral upset. Just a thought though.
I'd say the chaeto has stalled in growth. It's a nice green color (not white or too dark). But it's not really growing much anymore. I haven't harvested any of it yet.
So it was growing and has halted, but the water is definitely testing and showing nutrients - which micro nutrients are you suggesting are stripped? I was going to do an icp test tomorrow and send it off.
What kind of light are you using to grow chaeto? If it's a cheap gro-light from the gardening store, it may not be able to grow chaeto fast enough to make a difference.
I'm using this light-
It's a full spectrum 200w fixture.
【Optimal Full Spectrum LED Grow Light】CANAGROW COB LED Grow Light with the optimal full spectrum(380-800nm) which provides plants Veg and Flower all stages with everything they desire in the natural sunlight. Especially RED(630-660nm): Promote flowering and fruiting and increase yield directly; BLUE(440-460nm): Promote germination and photosynthesis; IR(780-800nm): Promoting plant cell growth; UV(380nm): Sterilization and disinfection.