Phosphate limited with Refugium - Help Please

[dubmaneh]

My system is P04 limited. Need some advice on how to fine tune my refugium to my stocking and feeding levels. Not looking to chase numbers but my corals aren't happy and I need to correct. Just not sure of the best course.

Last week parameters:
N03 - 5-10ppm (probably closer to 10ppm)
PO4 - 0.02ppm (Hanna ULR)

- Started feeding Reef Roids every evening to raise PO4. Which I believe spurred further growth in my cheato refugium and now....

Current parameters:
N03 - 5ppm (Salifert)
PO4 - 0ppm (Hanna ULR)

Roughly 10G refugium compartment in sump growing chaeto. Chaeto currently a solid brick with a 4hr photoperiod. No other nutrient sequestering/export methods. Do I just reduce the chaeto mass and thereby reduce nutrient uptake? Further reduce photoperiod? Or both?

 

[Randy Holmes-Farley Verified Community Expert]

I’m not sure there is any balancing possible, based just on an refugium, and I’d scale and light the refugium to manage nitrate. Phosphate may, at the moment, be mostly binding to rock and sand, and dosing (or feeding more) may be needed.

 

[dubmaneh]

Thanks Randy. I'll harvest 1/2 the chaeto, cut back the photoperiod and see what happens this week.
I swear Siporax and GFO are far easier to find the sweet spot with!