PO4 elimination and GFO consumption c

[ReefLab]

is this typical for PO4 levels after adding GFO? 2.39ppm recorded on 12/6 (added GFO) .74ppm 12/10. 0.5ppm on 12/15 and 0.26ppm today

is the gfo exhausted and PO4 decline due to uptake from the refugium?

 

[ReefLab]

Bump

 

[Tampaman]

I can say my PO4 is 0 with an overboard fuge...

 

[GabeM]

Maybe, how much did you add and what is the voume of water? I would be more concerned with the fluxuations in your parameters. I only run my gfo 6 hours a day during the dark to clean up after feeding.

 

[lapin]

......
Is the gfo exhausted and PO4 decline due to uptake from the refugium?

GFO exhausted; It depends on the rate of flow, the amount of GFO per gallon and Po4 levels. When new, GFO is at its peak and weakens with age (useage).
Ideally you want a slower flow so it last a month and pulls out Po4 at a slower rate.
How much the fuge comes into to play depends on whats in the fuge using Po4. Also dont forget water changes might effect levels.

 

[Randy Holmes-Farley Verified Community Expert]

There’s no mathematical way to know it is depleted except that it stops dropping. GFO can deplete very fast at 2 ppm phosphate.
Bear in mind that most phosphate is likely bound temporarily to rock and sand, so to drop a reef tank from 2 ppm to 1 ppm takes far more than in an identical volume of just seawater.

 

[ReefLab]

GFO exhausted; It depends on the rate of flow, the amount of GFO per gallon and Po4 levels. When new, GFO is at its peak and weakens with age (useage).
Ideally you want a slower flow so it last a month and pulls out Po4 at a slower rate.
How much the fuge comes into to play depends on whats in the fuge using Po4. Also dont forget water changes might effect levels.

Thank you for responding. Do you think because of the high initial level, regardless of flow it will be depleted very quickly? I do have a gate valve but its hard to gauge the flow in the reactor. There was a 20% water change between the two most recent values so that of course contributes to some of the phosphate decline. Just to note, i'm using sea lettuce in my refugium. Its growing very quickly but my sump (15% of total volume) is only about half full of the sea lettuce

There’s no mathematical way to know it is depleted except that it stops dropping. GFO can deplete very fast at 2 ppm phosphate.
Bear in mind that most phosphate is likely bound temporarily to rock and sand, so to drop a reef tank from 2 ppm to 1 ppm takes far more than in an identical volume of just seawater.

Ok that's what i was thinking. I think I'll stop running the GFO and see what the levels do.. The slow decline at this point i'm thinking is likely due to the refugium macro growth and skimmer. Would you agree?
I'd like to get the level below .05, however my nitrate level is stubbornly at around 15ppm so i don't want to decrease phosphate too quickly.

 

[Randy Holmes-Farley Verified Community Expert]

Slow is good. It is much worse to be too low than too high due to risk of dinos.