Po4 increase suddenly

[JonasRoman]

This is maybe not a primary chemical matter. So administrator can relocate this post if they want. I just want to illustrate, but also ask for inputs. It's good with discussions. The reason of this suddenly po4 increase with absolutely no obvious reason. The history is that I have had po4 around 0.02 for a very long time since one year back. Last month I could see and tendency to an increase to around 0.06, and now suddenly almost from 1 day to another it goes up to 0.11.
I have not increased the bioload and actually feeded a little less last week
I think this illustrate how unbalanced, sometimes our system is. Fascinating at same time. Maybe time to add carbon, NOW I believe my system may be carbon limited;-)

Nitrate around 2-3 ppm



Jonas

 

[sixty_reefer]

All reef aquariums are carbon limited in a way or the other, we don’t purposely encourage carbon cycles either, that would be to allow macro and micro algae’s to grow and instead of removing them allowing them to decompose in the system transforming inorganic carbon into organic carbon that in its turn would feed microbes and the so desired diversity and by effect lower N and P and produce Co2 completing a cycle ish.

In order to respond to your main question the most currently accepted reply in the hobby would be that your rock is leaching phosphate

 

[Dan_P]

This is maybe not a primary chemical matter. So administrator can relocate this post if they want. I just want to illustrate, but also ask for inputs. It's good with discussions. The reason of this suddenly po4 increase with absolutely no obvious reason. The history is that I have had po4 around 0.02 for a very long time since one year back. Last month I could see and tendency to an increase to around 0.06, and now suddenly almost from 1 day to another it goes up to 0.11.
I have not increased the bioload and actually feeded a little less last week
I think this illustrate how unbalanced, sometimes our system is. Fascinating at same time. Maybe time to add carbon, NOW I believe my system may be carbon limited;-)

Nitrate around 2-3 ppm



Jonas

I reviewed the data. The change looks too small to to be statistically significant. We cannot reject the null hypothesis that no change has occurred.

To improve the statistical power, you could take multiple readings each day. Since your situation is not critical, you can just continue trending the data another week or two. I would resist the temptation to fix something that is not a problem.

 

[JonasRoman]

All reef aquariums are carbon limited in a way or the other, we don’t purposely encourage carbon cycles either, that would be to allow macro and micro algae’s to grow and instead of removing them allowing them to decompose in the system transforming inorganic carbon into organic carbon that in its turn would feed microbes and the so desired diversity and by effect lower N and P and produce Co2 completing a cycle ish.

In order to respond to your main question the most currently accepted reply in the hobby would be that your rock is leaching phosphate

I doubt its my rock. Its not living rock (coraroc) established 18 months ago. Why should that suddenly leak PO4 when not leaked before? The pH is not lower than it always has been. In that case I would maybe succeed to bind back PO4 by raise pH some with CO2 absorber. At least could be interesting to try. Concerning C limiting, my tank has historically not been for sure carbon limited ( I have done som studies posted here), but yes, now it is for sure. I never dose carbon, and despite that I have had an almost optimal assimilation of N and P. I think my tank produce internal carbon sources to establish that balance, but now of some reason its not enough, and P is therefore not assimilated in same speed as before, and thats why my PO4 raise. Thats my theory at least. Maybe its just that easy that with increasing growth of fish metabolism, the P cycle needs more C to assimilate P?

/Jonas

 

[JonasRoman]

I reviewed the data. The change looks too small to to be statistically significant. We cannot reject the null hypothesis that no change has occurred.

To improve the statistical power, you could take multiple readings each day. Since your situation is not critical, you can just continue trending the data another week or two. I would resist the temptation to fix something that is not a problem.

I definitively agree with that, so lets see the pattern over some longer period. And yes, I will at least measure twice a day, and yes, I will not interact. I do not see this as a problem at all (so far) but just an interesting find. I will follow up :-)

Jonas

 

[sixty_reefer]

I doubt its my rock. Its not living rock (coraroc) established 18 months ago. Why should that suddenly leak PO4 when not leaked before? The pH is not lower than it always has been. In that case I would maybe succeed to bind back PO4 by raise pH some with CO2 absorber. At least could be interesting to try. Concerning C limiting, my tank has historically not been for sure carbon limited ( I have done som studies posted here), but yes, now it is for sure. I never dose carbon, and despite that I have had an almost optimal assimilation of N and P. I think my tank produce internal carbon sources to establish that balance, but now of some reason its not enough, and P is therefore not assimilated in same speed as before, and thats why my PO4 raise. Thats my theory at least. Maybe its just that easy that with increasing growth of fish metabolism, the P cycle needs more C to assimilate P?

/Jonas

Dissolved organic carbon (C) is only a limiting factor for microbes if N and P is on the rise. P alone on the rise could mean several things in your particular situation, for example N could be a limiting factor, do you have a history of Nitrate also?

There is multiple things I can think of that can make P rise in reef aquariums.

 

[JonasRoman]

Dissolved organic carbon (C) is only a limiting factor for microbes if N and P is on the rise. P alone on the rise could mean several things in your particular situation, for example N could be a limiting factor, do you have a history of Nitrate also?

There is multiple things I can think of that can make P rise in reef aquariums.

Good point. Nitrate is not changing ( so far), it circles around 2-3 ppm. Measure once a day. Never reach zero. But based on the ratio N/P now (42), if I start to dose carbon in excess, I would say nitrate will soon be the limiting factor.

 

[sixty_reefer]

Good point. Nitrate is not changing ( so far), it circles around 2-3 ppm. Measure once a day. Never reach zero. But based on the ratio N/P now (42), if I start to dose carbon in excess, I would say nitrate will soon be the limiting factor.

In that situation I’d just monitor and if phosphate keep rising I would just implement a method that would only target phosphate export.
There is no advantage to take the hole tank out of balance with additional DOC in order to straighten the line on phosphate imo.

 

[Staghorn]

Can you provide your alkalinity numbers during these dates as well?

 

[JonasRoman]

In that situation I’d just monitor and if phosphate keep rising I would just implement a method that would only target phosphate export.
There is no advantage to take the hole tank out of balance with additional DOC in order to straighten the line on phosphate imo.

That is exactly what I also think and will do if it continues to increase.

 

[JonasRoman]

Can you provide your alkalinity numbers during these dates as well?

Its stable and circle around 8,0 dKH, and no increase of Ca/Alk consumption.