Dosing Phosphates to Reduce Nitrates?

[Blue Carbon Reefing]

Sorry for the long rant but I want give as much background information as possible and I could not find anything specifically through a search here so I am reaching out to the experts for help. I have a 1200+ Gallon total water volume system (only about 500 Gallons is stocked with fish and coral) that has been set up now for over 3 years that Nitrate and Phosphates are way out of wack. I have been trying to reduce Nitrates only as my Nitrates were around 100 PPM for about a year now. My Phosphates have always been in the good range between .01 to .07 is the highest I have ever seen. Typically .03-.04. I have had a huge outbreak of what I believe is Dino's. I don't have a microscope to confirm but it is all over everything that gets lit. I did just get some ICP test results back from ATI I am happy to share if needed but I tested in Oct 2018 and My nitrates were 114.4 mg/l and Phosphate was .05 mg/l. Now today I just received my next analysis and my Nitrates are up to 157.5 mg/l and my Phosphates are undetectable, phosphorus is only 3.18 ug/l. I have tried have tried carbon dosing (both vinegar and vodka dosing) and stopped. I currently have a pretty big nitrate reactor set up with 16lbs of sulfur media which will come out at zero Nitrate effluent but only if I keep the flow rate at about 1 drop per second. If the flow is turned up at all the effluent is coming out closer to the tank level of over 80 PPM on an API Checker. I also have a 150 Gallon Refugium as part of the system with about a 5 gallon bucket worth of Chaeto in it but growth has slowed which I think is because there is no phosphate in the water or the plague of Dinos has eaten it all. I do, per Randy's suggestion dose Manganese and Iron. On the most recent ATI Results Iron was up to 12.99 ug/l and Manganese was undectable.

I would be happy to go into anything else you think might be important to answer the questions below. I have thought about feeding heavier but my fear is the foods I feed, is just as high in nitrates as it is phosphates. I feel like my system is set up to effectively remove phosphate but not nitrate and I am unsure what to do from here.

So here are my questions.

Why after months of running a Sulfur Denitrator can I not turn up the flow to run more water through it to eliminate just nitrate? What is the limiting agent to feed the nitrifying bacteria?

How do I get nitrates down from 157.5 MG/L without doing thousands of gallons of water changes?

Would dosing Phosphate help feed the chaeto growth and will that be effective in bringing Nitrates down?

Does Chaeto take out a significant amount of Nitrates of the water?

Moving forward what do I change my system to reduce help keep Nitrates low?

Thank you for any advice or suggestions!

 

[Big G]

Does Chaeto take out a significant amount of Nitrates of the water?

Yes. It can be almost too good at removing nitrates. I use a mix of chaeto and sea lettuce in my sump and light the sump the opposite hours of the DT. Then there is a fine balance of just enough frozen food fed to my fish each day to keep nitrates and phosphates low but not bottoming out and causing all kinds of algae problems. For example, I always thaw the frozen foods and pour off the excess liquid to prevent phosphate spikes. But doing that, if I didn't feed enough the nitrates and phosphates dropped to undetectable levels - not good. Lesson learned. Algae growth was crazy fast and everywhere.
It didn't take much or too long for the levels to drop so low. I was amazed. And then the chaeto and sea lettuce began to dwindle.

So, I still pour off the liquid but I feed more. Chaeto and sea lettuce grew back to healthy levels. And Nitrate and phosphate levels are right where they need to be. At least so far LOL

 

[Blue Carbon Reefing]

@Randy Holmes-Farley

Why after months of running a Sulfur Denitrator can I not turn up the flow to run more water through it to eliminate just nitrate? What is the limiting agent to feed the nitrifying bacteria?

How do I get nitrates down from 157.5 MG/L without doing thousands of gallons of water changes?

Would dosing Phosphate help feed the chaeto growth and will that be effective in bringing Nitrates down?

Does Chaeto take out a significant amount of Nitrates of the water?

Moving forward what do I change my system to reduce help keep Nitrates low?

 

[saltyfilmfolks]

@Randy Holmes-Farley

Why after months of running a Sulfur Denitrator can I not turn up the flow to run more water through it to eliminate just nitrate? What is the limiting agent to feed the nitrifying bacteria?

How do I get nitrates down from 157.5 MG/L without doing thousands of gallons of water changes?

Would dosing Phosphate help feed the chaeto growth and will that be effective in bringing Nitrates down?

Does Chaeto take out a significant amount of Nitrates of the water?

Moving forward what do I change my system to reduce help keep Nitrates low?

Nitrifying bacteria need no3 and Po4 and an organic carbon source. As do corals.
With limited Po4 the bacteria can’t reproduce as well.
Dosing Po4 will , and possibly a small amount of a carbon source , will cause the bacteria to reproduce.
It will also feed the macros.

Bacteria and Chato both consume more no3 than Po4.

IMO , if you carbon dose it will bring down the no3 faster (as usual) but you should keep a close eye on Po4 levels and likely dose.

In honestly don’t see a reason you can’t turn up the flow to the denitrator.

As I understand it , most organic carbon comes from foods as the waste produced. It’s likey that it’s both the carbon and the Po4 that may be limited.

However, you should also definitely look to see why your no3 is sooo high. There’s no real relationship ship between the two but that sure seems odd.

 

[Dan_P]

Why after months of running a Sulfur Denitrator can I not turn up the flow to run more water through it to eliminate just nitrate? What is the limiting agent to feed the nitrifying bacteria?

How do I get nitrates down from 157.5 MG/L without doing thousands of gallons of water changes?
Would dosing Phosphate help feed the chaeto growth and will that be effective in bringing Nitrates down?
Does Chaeto take out a significant amount of Nitrates of the water?
Moving forward what do I change my system to reduce help keep Nitrates low?

Thank you for any advice or suggestions!

Your system could be phosphate limited. While 0.03 ppm is typically the answer to what is a good level for phosphate, it is an incomplete answer to the question. The complete answer is enough phosphate for your system’s needs plus 0.03 ppm left over. Since it would difficult or impossible to predict what is actually needed, you will need to figure it out empirically.

It seems one of the needs of your system is nitrate removal. I don’t have experience with sulfur denitrators, but I have run small scale carbon dosing experiments demonstrating how nitrate consumption can slow or stall by being phosphate limited and start right up again with the addition of phosphate. This was no great discovery in bacteriology, but a revelation to me about how important phosphate is to bacteria.

Recently, I have started macro algae nutrition studies. I am still learning to grow alga in a bottle, but already the importance of phosphate has been made clear to me. My GHA are phosphate sponges. Algae also need iron. In my second culture of GHA, nitrate reduction was going along slowly while phosphate was being vacuumed up. I also remembered Randy’s suggestion about iron. So I raised the level to 0.25 ppm with iron gluconate. Bang, the next day 20 ppm nitrate was gone. I had a decent size clump of GHA, but still, the rate enhancement was startling.

I am sure someone will give you advice on tweaking a sulfur denitrator, but in regards to carbon dosing and growing algae, I would consider dosing phosphate as part of your options. The idea is to dose phosphate to give bacteria or algae enough to grow and expand their need for nitrate. One hitch in this process is that if your system has aragonite sand and rocks, they too will adsorb phosphate until they are saturated. Just keep dosing, but monitor your phosphate level. This is no time to economize on testing.

With regards to Chaeto, water flow is important as is the right level of light. Too little light and it won’t grow. Too much and you’ll get photo inhibition and kill it. Unhealthy algae will harbor all sorts of organisms including cyanobacteria. A heathy alga isn’t a home to many hitchhikers.

 

[Salps]

Whatever you do, I recommend not running N or P down to zero and keeping it there. I carbon dosed my tank down to that. What I got out of it was a clean tank and dying corals. I had to dose N & P for several weeks before the numbers would regulate themselves. In the long run I keep my numbers around .05 ppm Phosphate and 5 ppm Nitrate with the corals being much happier for it. I let carbon be my limiting factor that I can add if needed. Yes, I get a little algae but keeping my water numbers in check, keeps the grow rate of algae manageable for the clean up crew.

 

[SeaDweller]

@Randy Holmes-Farley

Why after months of running a Sulfur Denitrator can I not turn up the flow to run more water through it to eliminate just nitrate? What is the limiting agent to feed the nitrifying bacteria?

How do I get nitrates down from 157.5 MG/L without doing thousands of gallons of water changes?

Would dosing Phosphate help feed the chaeto growth and will that be effective in bringing Nitrates down?

Does Chaeto take out a significant amount of Nitrates of the water?

Moving forward what do I change my system to reduce help keep Nitrates low?

I’m having this issue with my sulfur reactor too. At 1-2 drops/sec on a broken in reactor/media I get 0.0 or close to 0.0 ppm NO3, but when turned up a bit, the readings are through the roof, but I’ve learned this is most likely NO2 messing up the reading as the NO3 to N2 conversion isn’t complete. So I’ve tested a few times when this has happened and about another day later, it’ll drop from the effluent. So I’m stuck at about 3-4 drops/sec; higher than this and I get messed up NO3 readings.

I have a 240 display with a 60 gallon sump and I calculated that my reactor processes like 3-4 gallons a day. It’ll take forever to come down. My NO3 was 200+. I did over 400 gallons worth of WC to bring it down to 25 and I think the reactor is taking care of NO3 cuz my NO3 in the display is now 10 ppm. But it could be a few other things that are helping it down too.

If you have a large reactor with 16 gallons of media, it’ll take some time to process and bring down 1200 gallons of water to help. Unfortunately I really feel you have to do large water changes to make a dent in your NO3. Good luck.

 

[Blue Carbon Reefing]

Thank you all for the advice. What is the best way to dose phosphate to the tank? Through a search I have seen others in the past dose Trisodium Phosphate by Loudwolf. Is that a good one to use? Any potential side effects I should look out for?

 

[SeaDweller]

Thank you all for the advice. What is the best way to dose phosphate to the tank? Through a search I have seen others in the past dose Trisodium Phosphate by Loudwolf. Is that a good one to use? Any potential side effects I should look out for?

I pondered dosing PO4 too, but based on your system volume and the red field ratio, I don’t think it’s the best approach ( I used the red field ratio calculator and it suggested doing large water changes for myself).

It may be close to impossible to want to do large water changes in your system, but I really don’t know of a quicker way to bring those levels down...

 

[Blue Carbon Reefing]

I pondered dosing PO4 too, but based on your system volume and the red field ratio, I don’t think it’s the best approach ( I used the red field ratio calculator and it suggested doing large water changes for myself).

It may be close to impossible to want to do large water changes in your system, but I really don’t know of a quicker way to bring those levels down...

I am not worried about bringing the levels down fast. I actually feel like that could do more harm than good. Nitrates have been high for a long time and the corals and fish are doing just fine. What I do want is to figure out how I can start bringing my Nitrates level down instead of them going even higher. I am hoping to figure out what my sulfur denitrator is missing so it can effectively bring down nitrates. Maybe carbon dosing has never done well for me because there isn't enough phosphate in the water for the carbon source to bond to. Maybe that is also why the nitrifying bacteria are remaining at minimal numbers in the sulfur denitrator.

 

[ATI North America]

We will soon be launching our Nutrition line in North America which is designed just for these types of questions. 3 different products will be available to dose: Carbon, nitrates and phosphates. Like our facebook page to stay in the loop if it is of interest.

 

[SeaDweller]

I am not worried about bringing the levels down fast. I actually feel like that could do more harm than good. Nitrates have been high for a long time and the corals and fish are doing just fine. What I do want is to figure out how I can start bringing my Nitrates level down instead of them going even higher. I am hoping to figure out what my sulfur denitrator is missing so it can effectively bring down nitrates. Maybe carbon dosing has never done well for me because there isn't enough phosphate in the water for the carbon source to bond to. Maybe that is also why the nitrifying bacteria are remaining at minimal numbers in the sulfur denitrator.

Why would PO4 have anything to do with the anaerobic bacteria in the sulfur reactor? I’m not sure they utilize PO4 in the conversion of NO3 into usable O to them and N as the byproduct?

So let’s assume your reactor works. I’d assume it just maintains your current tank level of 150 ppm and then just processes what new NO3 levels you’re adding. You need to bring the current level down... whether it be water changes or carbon dosing, possible PO4 dosing...

Also you ask why you can’t turn up the effluent of the reactor. You CAN. If your effluent is 0.0 ppm at whatever rate you’re running now, you’re supposed to turn it up, but you have to calculate how much it processes in a day. If it only processes 5-10 gallons a day let’s say, then that’s a long time to process 1200 gallons, just as an example.

 

[Blue Carbon Reefing]

Why would PO4 have anything to do with the anaerobic bacteria in the sulfur reactor? I’m not sure they utilize PO4 in the conversion of NO3 into usable O to them and N as the byproduct?

So let’s assume your reactor works. I’d assume it just maintains your current tank level of 150 ppm and then just processes what new NO3 levels you’re adding. You need to bring the current level down... whether it be water changes or carbon dosing, possible PO4 dosing...

Also you ask why you can’t turn up the effluent of the reactor. You CAN. If your effluent is 0.0 ppm at whatever rate you’re running now, you’re supposed to turn it up, but you have to calculate how much it processes in a day. If it only processes 5-10 gallons a day let’s say, then that’s a long time to process 1200 gallons, just as an example.

well as SaltyFilmFolks stated above nitrifying bacteria needs PO4 as well. That is why I am reaching out to the experts with a lot more chemistry background than I.

 

[SeaDweller]

well as SaltyFilmFolks stated above nitrifying bacteria needs PO4 as well. That is why I am reaching out to the experts with a lot more chemistry background than I.

Right, I get that. Maybe I’m assuming the anaerobic bacteria in the sulfur reactors you and I are running are different than the aerobic ones... let’s see if Dr Randy chimes in.

 

[Blue Carbon Reefing]

Ok I am opting to dose using Kh2PO4. My total water volume is estimated at 1250 Gallons. How many Tsp should I add to 1000ml of RO water to dose .02 PPM Phosphate in a 10ml solution? Using an online calculator it appears if I add 3 TSP to 1000ml of RO Water and dose 10ml I would be increasing my Phosphate by .02 ppm on my 1250 gallons system. Can anyone confirm my math is at least close? Also Is there a way to figure out how much Potassium I am dosing for every 10ml or 1000ml of solution as well?

Thank you!

Description

• Contains phosphorous (P) and potassium (K).
• Macronutrients essential for healthy plant growth and survival.
• 1 lb
• Guaranteed Analysis:
  
  
• Available Phosphate(P2O5) ....................52%
  
  
• Soluble Potash(K2O)............................. 34%
  

 

[Blue Carbon Reefing]

It's been 48 hours. bumping to confirm questions from above.. ☝☝