Carbon Dosing. PO4 Effect

[Dan_P]

I am conducting small scale carbon dosing experiments and came across what looks to be a strong and repeatable effect. I have seen discussions about the possible importance of PO4 in nitrate consumption during carbon dosing. Data in the graph below supports this notion. Each curve represents a different initial phosphate concentration. The phosphate concentration at the end of the experiment is undetectable. This data might explain why in some cases nitrate reduction seems to take forever or even stalls.

In this experiment design, I start with a sngle large dcarbon dose. Slight haziness but no massive bacterial blooms were ever seen with this approach.

I am wondering if dosing PO4 along with carbon might speed up nitrate removal. I might try this with my fish only system.

 

[RamsReef]

Thanks for your efforts,

However, when researching into doing carbon dosing I thought it was pretty common knowledge this happens.

I'd say the dangers with carbon is when you get near 0 nitrates and you dose or have phosphates, this is when you typically get more ugly breakouts, including but not limited too,

Cyano, Dinos, Diatoms.

Then when you try to correct for the nitrogen deficiency or ease up off the carbon you typically might see,

Bryopsis, GHA

 

[Dan_P]

Thanks for your efforts,

However, when researching into doing carbon dosing I thought it was pretty common knowledge this happens.

I'd say the dangers with carbon is when you get near 0 nitrates and you dose or have phosphates, this is when you typically get more ugly breakouts, including but not limited too,

Cyano, Dinos, Diatoms.

Then when you try to correct for the nitrogen deficiency or ease up off the carbon you typically might see,

Bryopsis, GHA

I agree that the anecdotal data is out there leads to the general idea about the need for phosphate during carbon dosing. I don’t think anyone has taken the time to quantify just how important it is. Your welcome

As for adding carbon in the presence of phosphate with low nitrate and bad things happening, I wonder how that idea would play out in the lab. I have been looking into culturing cyaanobacteria on a small scale and might test this idea. Keep the ideas coming.

 

[RamsReef]

Some people just want to watch the world burn

Good luck on your quest

 

[JimWelsh]

I find this pretty interesting. Good work!

 

[Dan_P]

I find this pretty interesting. Good work!

Thanks!

 

[Scrubber_steve]

I am conducting small scale carbon dosing experiments and came across what looks to be a strong and repeatable effect. I have seen discussions about the possible importance of PO4 in nitrate consumption during carbon dosing. Data in the graph below supports this notion. Each curve represents a different initial phosphate concentration. The phosphate concentration at the end of the experiment is undetectable. This data might explain why in some cases nitrate reduction seems to take forever or even stalls.

In this experiment design, I start with a sngle large dcarbon dose. Slight haziness but no massive bacterial blooms were ever seen with this approach.

I am wondering if dosing PO4 along with carbon might speed up nitrate removal. I might try this with my fish only system.

Interesting. Well done.
I have to ask; what are you using to measure po4 & no3?
How many tests were carried out at each po4 value? & how much variation was there between each test run at each specific po4 value? Whats the error values?

There's not a huge difference in no3 reduction between a po4 values of 0.07 & 3 times that amount. All runs show good no3 reduction.
Making sure po4 doesn't bottom out is the more important factor I think.

cheers

 

[Dan_P]

I have to ask; what are you using to measure po4 & no3?

PO4: Hanna Checker, ULR
NO3: Red Sea Pro chemistry, Hanna LR PO4 Checker or Total Cl2 Checker for color intensity

How many tests were carried out at each po4 value? & how much variation was there between each test run at each specific po4 value? Whats the error values?

Each point is the average of two separate experiments. Surprisingly, for a biology experiment the values were within 10% of each other. This was an exploratory experiment. More work is being planned.

There's not a huge difference in no3 reduction between a po4 values of 0.07 & 3 times that amount. All runs show good no3 reduction.
Making sure po4 doesn't bottom out is the more important factor I think.

Agreed, 2 vs 4 days is not much. I don’t know how this plays out with small daily dosing, whether the difference is magnified or not. My dose was very large. The shape of the curves may be of interest. The two lower concentration curves appear to be “S” shaped, a lag in the beginning and stalling at the end. Might be of diagnostic use.

I have been wondering whether a small scale test could be used to predict how to dose your system rather than blindly stepping up dosing amounts until something good happens.

 

[taricha]

That’s excellent. I think it’s interesting that in all three of your runs most hobbyists testing those PO4 values would conclude that they had “plenty” of P, yet the N reduction rate was clearly varied by the amount of P even at those high values.
I think the hobby conventional wisdom would have said you’d need PO4 well under those numbers before rates of N consumption were affected negatively.
And a Q: in this setup the consumption of N & P is being largely done by bacteria/biofilter?
Asking because in mine, I’d say such reductions are more algae etc.

 

[Dan_P]

That’s excellent. I think it’s interesting that in all three of your runs most hobbyists testing those PO4 values would conclude that they had “plenty” of P, yet the N reduction rate was clearly varied by the amount of P even at those high values.
I think the hobby conventional wisdom would have said you’d need PO4 well under those numbers before rates of N consumption were affected negatively.
And a Q: in this setup the consumption of N & P is being largely done by bacteria/biofilter?
Asking because in mine, I’d say such reductions are more algae etc.

Thanks for the recognition!

Yes, we might be underestimating the PO4 level needed by bacteria to quickly consume nitrate. I hope to get a better feel for this when I run full scale aquarium dosing.

My small scale experiments are run without substrate unless it is a variable I am testing. Since the test vessels are covered with aluminum foil, I presume all nitrate and phosphate consumption is being done by heterotrophs, probably bacteria, though yeast, fungi and protozoa might be participating as well.

I have been catching up on reading about marine bacteria nutrition. It seems that nitrate consuming heterotrophic bacteria might be playing a bigger role in the ocean than originally thought. The same might be happening in aquaria as well. We might be giving algae too much credit for PO4 and NO3 consumption

 

[taricha]

I have been catching up on reading about marine bacteria nutrition. It seems that nitrate consuming heterotrophic bacteria might be playing a bigger role in the ocean than originally thought. The same might be happening in aquaria as well. We might be giving algae too much credit for PO4 and NO3 consumption

Possibly, and it looks like measurements on my system are kind of a flip side to what you're showing here: Much of my nutrient export is algal - and my system reduces in the ballpark of just over 2 ppm NO3 per day like what you show here. But the flip side is I haven't ever gotten near the 0.1 ppm/day PO4 drop that your system showed.

 

[Dan_P]

Possibly, and it looks like measurements on my system are kind of a flip side to what you're showing here: Much of my nutrient export is algal - and my system reduces in the ballpark of just over 2 ppm NO3 per day like what you show here. But the flip side is I haven't ever gotten near the 0.1 ppm/day PO4 drop that your system showed.

I am going to start dosing my aquarium again. This will give me a chance to perform a reality check on my small scale experiments.