High P, Low N -- KNO3 vs. Carbon dosing.

[larcat]

Hi Doc Holmes-Farley,

I've waded through lots and lots of vodka reading, and am pretty familiar with the ideas around this or that limiting growth of this or that in aquaria from my planted experience.

Without going into massive detail on our reef setup -- We've got bottomed out N (with some algae and solid export via mature siporax), heavy skimming, very very little build of of detritus, and no dedicated P export and high P (~.15-.2) We don't want to do GFO.

We've considered carbon dosing, but with N as a limiter, I'm not convinced P uptake would happen. Is there a good reason not to dose 2-3 ppm N via KNO3. Test N/P. Wait. Test. Wait. If P goes down and N stays bottomed, continue till P problem is gone, if N begins to accumulate and P stays where it is, stop dosing.

My understanding from what you have written is that unless we did this long term, the addition of K wouldn't be an issue.

Finally, is it reasonable to think that this will help bring down our P and help with the hair algae issue?

Thanks much,

-L

 

[HolisticBear]

Just jumping in while you're waiting for the doctor.

We've considered carbon dosing, but with N as a limiter, I'm not convinced P uptake would happen

Seems a reasonable assumption.

We don't want to do GFO.

You likely already considered it and rejected it, but there are the other options including aluminum based media (Phosguard) or lanthanum chloride (Phosphate RX)

Following the thread. As you already know, you don't want 0.0 NO3, so I'm guessing the crowd will recommend NO3 dosing (or reduced exported)

 

[BlueCursor]

I was N limited for a while (too much carbon dosing). I found adding NO3 did lower P04. It also did wonders for controlling algae because the higher NO3 forced down P04. I used KNO3 and never had an issue with high K.

Based on my experience, being N03 limited is worse than being PO4 limited.

 

[larcat]

You likely already considered it and rejected it, but there are the other options including aluminum based media (Phosguard) or lanthanum chloride (Phosphate RX)

Following the thread. As you already know, you don't want 0.0 NO3, so I'm guessing the crowd will recommend NO3 dosing (or reduced exported)

Thanks for jumping in

Don't want to do aluminum based media. We've got a bunch of lanthanum sitting around, and I've thought about it, but I'm not super keen on adding it with live stock in the tank. It's pretty remarkable stuff though.

I'm not worried about imminent too-low-nutrients at the moment, and everything in the tank currently likes to eat with it's mouth so we can always feed heavier

I was N limited for a while (too much carbon dosing). I found adding NO3 did lower P04. It also did wonders for controlling algae because the higher NO3 forced down P04. I used KNO3 and never had an issue with high K.

Based on my experience, being N03 limited is worse than being PO4 limited.

Great to hear! Can you talk about your regimine? We have ~ 50 gallons of water. We mixed 2 tsp + a smidge of KNO3 in 150 ml RO, and dosed 10 ml of that solution, which should raise N by ~ 2.6 ppm. Gunna wait 24 hours and test. We're borrowing one of the quasi-lab-grade Hannah bench phos testers from a friend, and using Salifert for N.

 

[Randy Holmes-Farley Verified Community Expert]

It might bring down P, but to do that it needs to spur some balanced uptake method, and in your case, that might be the algae.

 

[larcat]

Thanks very much for the reply! I was thinking/hoping the bacteria bed we have in our siporax would do some of the munching, assuming we aren't carbon limited.

What would you suggest, given we aren't trying to have a high ph, high tds planted tank

It might bring down P, but to do that it needs to spur some balanced uptake method, and in your case, that might be the algae.

 

[Randy Holmes-Farley Verified Community Expert]

The goal is the deal with the algae?

How are the other organisms?

 

[larcat]

The goal is the deal with the algae?

How are the other organisms?

First -- Thank you for the help.

Organisms (dendros, acans, 1 bta, ricordia, fishes, small inverts) are at worst solidly stable, at best growing rapidly depending on the coral. Clowns are spawning regularly.

Goals are:

1) Algae removal.
2) Eventual acropora introduction. Tester frags (very small, from a trusted source) lasted about 5 weeks a couple months ago. I assume phos levels are mostly to blame.

 

[Hans-Werner]

In my opinion NO3 is not the best nitrogen compound to achieve this but you may give it a try. Ammonium is the preferred nitrogen form for corals and algae but it is toxic in higher concentrations. Amino acids are nitrogen and organic carbon at the same time and similar to ammonium but non-toxic. Urea also is similar to ammonium and non-toxic.

 

[larcat]

Well we tested last night, 24 hours after dosing. N detectable but barely (vs. not detectable before) and PO4 down to .1

Maybe not causal, but....

In my opinion NO3 is not the best nitrogen compound to achieve this but you may give it a try. Ammonium is the preferred nitrogen form for corals and algae but it is toxic in higher concentrations. Amino acids are nitrogen and organic carbon at the same time and similar to ammonium but non-toxic. Urea also is similar to ammonium and non-toxic.

If I knew how to measure AA nitrogen, I might have tried that. KNO3 is safe for fish and coral is small amounts, easy to dose accurately, and we have it laying around for our planted tanks.

 

[Hans-Werner]

I do not doubt that it works with nitrate, especially if phosphate is high. I think if you compare the corals look better (polyp extension etc.) with other forms of nitrogen and in my experience nitrate interferes with low phosphate concentration which was not your problem. I would recommend not to use nitrate when at the same time phosphate concentration is low, especially not with Acropora and Montipora. I think .15 to .2 PO4 is not to blame for lack of succes with Acropora but give it a try too. I think .1 ppm PO4 is optimum for Acropora growth.

Did you combine potassium nitrate with vodka or without vodka?

 

[BlueCursor]

I actually see more algae when my system is NO3 limited. To make matters worse, the algae I see is bad kinds, not the green film algae.

When I keep NO3 detectable, I do see more green film algae and less of the troublesome algae. In fact, if I keep NO3 at 2+ ppm, my algae issues go away. I do keep a refugium. So the plants are taking up other nutrients I assume. I also dose iron to keep green corals green, so I doubt I have an iron limit.

For me, being NO3 limited probably hinders my plant export method. I also had the same issues with bad algae vs limited algae or a little of the good algae even before adding a refugium. Back then I was running biopellets. They kept my NO3 at 0, PO4 was too high, and bad types of algae were killing me.

Edit: I'll probably get asked, so to clarify I consider green film algae a healthy algae and easy to deal with. Hair, brush, and basically all furry algae is a pain to deal with because CUC tend to not eat it.

 

[larcat]

Really interesting, thanks for the post..

In our case, no refugium at the moment. We've realized we need some sort of P export, and aren't willing to do GFO, so we are currently debating between Vodka and getting a fuge going again. I think we both are biased towards fuge, but our old one became a detritus trap, and on this reboot (about a year in at this point), one of our guiding lines was minimizing detritus build up.

The chaeto reactors are an interesting idea, but I'm nervous about submersing LED without a turnkey solution, and the off the shelf reactors are expensive.

By green film you mean what we would call green dust algae in the fresh water planted tank world -- I.E the hard, super thin algae deposits that occur on hardscape and glass?

I actually see more algae when my system is NO3 limited. To make matters worse, the algae I see is bad kinds, not the green film algae.

When I keep NO3 detectable, I do see more green film algae and less of the troublesome algae. In fact, if I keep NO3 at 2+ ppm, my algae issues go away. I do keep a refugium. So the plants are taking up other nutrients I assume. I also dose iron to keep green corals green, so I doubt I have an iron limit.

For me, being NO3 limited probably hinders my plant export method. I also had the same issues with bad algae vs limited algae or a little of the good algae even before adding a refugium. Back then I was running biopellets. They kept my NO3 at 0, PO4 was too high, and bad types of algae were killing me.

Edit: I'll probably get asked, so to clarify I consider green film algae a healthy algae and easy to deal with. Hair, brush, and basically all furry algae is a pain to deal with because CUC tend to not eat it.

 

[Randy Holmes-Farley Verified Community Expert]

I doubt adding a nitrogen source will deter the algae.

 

[Hans-Werner]

+1. I think especially Bryopsis and some other green algae are nitrophilic which means they love nitrogen compounds like nitrate. Bubble algae store extreme amounts of nitrate in the inner of the bubble. You can check this with any nitrate test.

 

[Big E]

I actually see more algae when my system is NO3 limited. To make matters worse, the algae I see is bad kinds, not the green film algae.

When I keep NO3 detectable, I do see more green film algae and less of the troublesome algae. In fact, if I keep NO3 at 2+ ppm, my algae issues go away. I do keep a refugium. So the plants are taking up other nutrients I assume. I also dose iron to keep green corals green, so I doubt I have an iron limit.

For me, being NO3 limited probably hinders my plant export method. I also had the same issues with bad algae vs limited algae or a little of the good algae even before adding a refugium. Back then I was running biopellets. They kept my NO3 at 0, PO4 was too high, and bad types of algae were killing me.

Edit: I'll probably get asked, so to clarify I consider green film algae a healthy algae and easy to deal with. Hair, brush, and basically all furry algae is a pain to deal with because CUC tend to not eat it.

Yes, these are the same experiences I had........these backwards type levels let certain cyano & pest algae thrive.
More traditional ratios were more conducive to good coral growth and common film algae that snails can control.

Since I've been tracking ratios they seem more important, especially for dominant Acropora systems.

 

[Big E]

In my opinion NO3 is not the best nitrogen compound to achieve this but you may give it a try. Ammonium is the preferred nitrogen form for corals and algae but it is toxic in higher concentrations. Amino acids are nitrogen and organic carbon at the same time and similar to ammonium but non-toxic. Urea also is similar to ammonium and non-toxic.

Yup, my take on this........a good fish population is important.........they are the perfect dosers.

 

[larcat]

We've decided to go the carbon route for export -- we have no dedicated P export at the moment, don't like GFO and have had very mixed experienced with growing chaeto in the past.

We do have a heavy fish load, so my hope is knocking the algae on its heels through aggressive removal in concert with carbon dosing will lead to decent lowering of P. Right now, though our Siporax probably gets some N out, I'm thinking that the hair algae is also gobbling a bit of N. Our P levels are high, but not insane. At that point, we can explore additional KNO3 or aminos is we are still imbalanced.

Sound like a decent plan, given our aversion to certain P export techniques?

 

[hart24601]

Why don't you like gfo?

 

[larcat]

We found it a real PITA to get the tumble dialed in so it didn't clump, and didn't spew gfo dust everywhere.

Why don't you like gfo?