0 Nitrates so I dosed Sodium Nitrate

[LV3]

Seems this is a popular topic lately and with BRSTV's episode on chaeto and refugium lighting I thought I would share my experience with low nitrates. About 45 days ago I switched over to the Kessil H380 and started growing chaeto like it was my job. Not knowing when I should prune it, I let it grow until it consumed the entire area in my sump. At the time I was still skimming and pulling out some real dark skimmate. I was also running GFO in a BRS reactor. My NO3 and PO4 were undetectable using the Red Sea kit and I thought that was good until a lot of my corals started losing color.

The color was fading slowly, zoas were peeking, still had decent PE on my acros so I thought things were OK for the most part. The tank had some small diatom looking patches but overall was looking pristine, no nuisance algae and the glass rarely developed a film that needed scraping. When the color loss became more noticeable in my LPS I decided that it must be the low NO3 in the system. So I tried feeding more, and more and more, until the point where I was feeding 1 cube of mysis and 1 cube of brine in the morning, Reef chili in the morning and when the lights when out. Red Sea's reef energy part A and B at 8mL daily. All this and the NO3 was still reading 0.

Recently I stopped skimming entirely, stopping running GFO and thought I would let the tank find the equilibrium on its own. Still with that feeding schedule above I couldn't get the NO3 to budge, at least to a point where I could register a reading on the test kit. Corals looking pastel, and no longer vibrant and rich in color, I thought I'd give the Sodium Nitrate a try. I couldn't bring myself to dosing stump remover into my system, despite the success of others, something about it made me weary.

I mixed up a solution today and dosed 6mL to the system. This may be anecdotal at this point, but zoas are opening, even those that were peeking for the last month and a half are laid open flat and big, there's good PE, and overall there is a noticeable difference in the colors. For those who dose or have dosed NO3 to their systems, have you noticed a quick response in the coral's color? The plan is to watch it a few days, continue testing and dose as needed to keep a steady balance at 5ppm. I'm thinking I'll see what the consumption looks like in another 24 hours and depending on what that looks like, either bring the skimmer back on line and/or increase my refugium lighting period back up the few hours I decreased it a while back.

Last, if anyone can explain the relationship between PO4 and NO3 in the system I think that would be helpful for me. I feel as though in the last 45 days or so I was chasing one or the other until I finally got fed up and took both the skimmer and GFO reactor offline and thought I would let it handle the levels on it's own. Would love to hear your thoughts.

Some details on my system:

Setup
==================
40g Breeder (mixed reef)
30g sump
Kessil AP700 (11" off the water, peaks at 30%)
SCA 65g rated skimmer
BRS mini GFO/Carbon reactor
Vectra M1
Marine Pure Block
Kessil H380 Magenta grow light

Water Params
==================
78 degrees
1.026
Ca 420ppm
Alk 9.0 dKh
Mg 1380
NO3 (now 5ppm)
PO4 .04-.05

 

[71xlch]

When I switched carbon dosing to a fuge I used postassium nitrate to feed nitrates until I got around 1ppm and I was weened off carbon dosing. I noticed results within 3 days of dosing enough to get 1ppm.

 

[slim_santa_chris]

When I switched carbon dosing to a fuge I used postassium nitrate to feed nitrates until I got around 1ppm and I was weened off carbon dosing. I noticed results within 3 days of dosing enough to get 1ppm.

like the supplement used in planted tanks?

 

[LV3]

When I switched carbon dosing to a fuge I used postassium nitrate to feed nitrates until I got around 1ppm and I was weened off carbon dosing. I noticed results within 3 days of dosing enough to get 1ppm.

Now, do you continue to dose potassium nitrate to keep the NO3 at 1ppm or will it stay there now on its own? Just wondering if I should expect to occasionally dose NO3 if the issue I have is that I can't get a sizable concentration of NO3 before it is consumed by the system.

 

[71xlch]

like the supplement used in planted tanks?

Yes

 

[71xlch]

Now, do you continue to dose potassium nitrate to keep the NO3 at 1ppm or will it stay there now on its own? Just wondering if I should expect to occasionally dose NO3 if the issue I have is that I can't get a sizable concentration of NO3 before it is consumed by the system.

I feed heavier to keep some nitrate. As long as there is a tint on the API test I'm happy. Corals seem to be as well. Chaeto/culpera mix is growing and things are coloured up.

I had a good 3-4 months with good colour and growth with carbon dosing. Started a new food mix and the balance was thrown off, phosphate and nitrate hit 0 for 6 weeks and stuff suffered. Life got busy and the tank suffered. Hoping a fuge is less walking a fine line. Time will tell.

 

[jwshiver]

When I started my tank I fell into the trap of keeping NO3 and PO4 at 0 and my corals lost all of their color. I recently started using Brightwell Aquatics nitrate http://www.bulkreefsupply.com/neonitro-balanced-nitrogen-supplement-brightwell-aquatics.html and occasionally phosphorus http://www.bulkreefsupply.com/neophos-balanced-phosphorus-supplement-brightwell-aquatics.html additives. The one thing I would recommend is to bring your alkalinity dkh down to between 7 -8 while running low nutrients. IMO nitrate at 5 is still considered low nutrient. My personal experience has been ULNS / low nutrients with alkalinity above 8 and high light do not play well together with SPS. You will see this reading other threads as well. I recently started to keep my nitrate at 5, and I have notice gradual overall improvements with my coral. I read one thread where it took 2 months for corals to color up after bring NO3 from 0 to 5 and PO4 up from 0 to 0.03

 

[Randy Holmes-Farley]

Last, if anyone can explain the relationship between PO4 and NO3 in the system I think that would be helpful for me. I feel as though in the last 45 days or so I was chasing one or the other until I finally got fed up and took both the skimmer and GFO reactor offline and thought I would let it handle the levels on it's own. Would love to hear your thoughts.

Both are added by all foods, and both are used by all photosynthetic organisms in a reef. If one runs out, organisms may grow more slowly or not at all, reduce uptake of the other.

 

[BlueCursor]

For my tank, if I keep nitrate up above 2 ppm, I rarely have a phosphate issue and it stays in the 0.02-0.03 range usually without GFO. Seems in my tank nitrate can easily become the limiting factor. When nitrate is the limiting factor, I have algae issues.

 

[Rob Lion]

Last, if anyone can explain the relationship between PO4 and NO3 in the system I think that would be helpful for me. I feel as though in the last 45 days or so I was chasing one or the other until I finally got fed up and took both the skimmer and GFO reactor offline and thought I would let it handle the levels on it's own. Would love to hear your thoughts.

@LV3 I think what you are looking for is the Redfield Ratio, this is the ratio at which most sea life grows at, like algae. it is;

(C) Carbon 106 : (N) Nitrogen 16 : (P) Phosphorous 1

Unfortunately, you can't easily measure the carbon, its locked up in organics or carbon dioxide CO2 etc, but we measure the Nitrogen from measuring Nitrates NO3 and phosphorous from measuring Phosphates PO4.

Simplifying this a little, that means that in an ideal tank for maximum growth, with carbon not being the limiting factor, your Nitrates should read 16 times higher than your Phosphates, i.e. Nitrates = 0.5 ppm, then Phosphates = 1/16 = 0.031 ppm, 1ppm NO3 = 0.062ppm PO4 etc.... If you are getting readings of zero Nitrates and zero Phosphates it generally means your tank (notably algae) has consumed them all due to an over abundance of available Carbon. If you limit the available carbon, then the N and P can't reduce more.

Generally, if your Nitrates to Phosphates ratio is greater than 16:1 (say 1ppm NO3 : 0.03ppm PO4) you tend to get algae issues, whereas if your Nitrates to Phosphates ratio is less than 16:1 (say 1ppm NO3 : 0.125ppm PO4) you get bacterial (cyano) issues.

This is why you will find that many different tanks can run on a higher Nitrate value, (say 10ppm NO3) because they also maintain a higher PO4 value to balance it at the 16:1 ratio, and/or they limit the production of algae or cyano by carefully controlling the free Carbon organics in their tank, i.e clean filters, clean sump, water changes, aggressive skimming, blowing off rocks, high water flow, siphoning substrate, removing anything dead asap etc etc.

This replays in the common "fixes" for tank issues,;
Carbon dosing ensures there is plenty of the right type of carbon compound available and will allow the beneficial bacteria to multiply fast, thus in turn breaking down the Nitrates down to Nitrogen that they need to live on, then filtering or skimming out this bacteria, but pretty much leaves the phosphates alone. If something isn't done about the phosphates, then cyano bacteria will prevail (otherwise know as red slime algae). The common fix for cyano is adding another bacterial type that targets and consumes the carbon available in the tank, so it can be filtered or skimmed out. And ofcourse we use GFO or Lanthanum Chloride to bind up phosphates that we then remove out of the system.

The temptation is often to INCREASE feedings to increase NO3 or PO4, but that increases Nitrogen and Phosphorous and Carbon , but in reality, you just have to REDUCE any free Carbon in your tank to see NO3 and PO4 rise. that's why many reefers use products like Dr Tims / Zeovit supplements etc, to control the carbon in the tank, which in turn stops the Algae AND Cyano issues, allows higher maintainable NO3/PO4 for coral growth/colour, as well as good husbandry to keep a "clean" system.

Personally, I would keep your refugium about half full of chaeto, leaving it room to grow. Feed less. Keep everything clean. only use GFO if needed. Skim 24/7.

With your NO3 of 5ppm and PO4 of 0.05ppm, you have 3 choices....

1. carbon dose to get your NO3 to equal 16 x 0.05ppm PO4 = 0.8ppm NO3
2. reduce / stop GFO use until PO4 = 5ppm NO3 / 16 = 0.31ppm PO4
3. if you reduce the free carbon in your tank as well, you should be able to make the carbon the limiting factor, so that you can hold your NO3 / PO4 at any desired levels, without having algae / cyano issues.

Having slightly too high NO3 is always better than too high PO4. Excessive PO4 browns out corals and slows growth.

Also, test kits (and us humans) are fairly in accurate, don't chase exact numbers too hard.... they are a guide to what we can reliably test / dose for.

There is another factor in coral coloration, and that is trace elements.... I have found that dosing the red sea colours ABCD greatly improves my coral colors, but KZ do a great range too.

 

[LV3]

@LV3 I think what you are looking for is the Redfield Ratio, this is the ratio at which most sea life grows at, like algae. it is;

(C) Carbon 106 : (N) Nitrogen 16 : (P) Phosphorous 1

Unfortunately, you can't easily measure the carbon, its locked up in organics or carbon dioxide CO2 etc, but we measure the Nitrogen from measuring Nitrates NO3 and phosphorous from measuring Phosphates PO4.

Simplifying this a little, that means that in an ideal tank for maximum growth, with carbon not being the limiting factor, your Nitrates should read 16 times higher than your Phosphates, i.e. Nitrates = 0.5 ppm, then Phosphates = 1/16 = 0.031 ppm, 1ppm NO3 = 0.062ppm PO4 etc.... If you are getting readings of zero Nitrates and zero Phosphates it generally means your tank (notably algae) has consumed them all due to an over abundance of available Carbon. If you limit the available carbon, then the N and P can't reduce more.

Generally, if your Nitrates to Phosphates ratio is greater than 16:1 (say 1ppm NO3 : 0.03ppm PO4) you tend to get algae issues, whereas if your Nitrates to Phosphates ratio is less than 16:1 (say 1ppm NO3 : 0.125ppm PO4) you get bacterial (cyano) issues.

This is why you will find that many different tanks can run on a higher Nitrate value, (say 10ppm NO3) because they also maintain a higher PO4 value to balance it at the 16:1 ratio, and/or they limit the production of algae or cyano by carefully controlling the free Carbon organics in their tank, i.e clean filters, clean sump, water changes, aggressive skimming, blowing off rocks, high water flow, siphoning substrate, removing anything dead asap etc etc.

This replays in the common "fixes" for tank issues,;
Carbon dosing ensures there is plenty of the right type of carbon compound available and will allow the beneficial bacteria to multiply fast, thus in turn breaking down the Nitrates down to Nitrogen that they need to live on, then filtering or skimming out this bacteria, but pretty much leaves the phosphates alone. If something isn't done about the phosphates, then cyano bacteria will prevail (otherwise know as red slime algae). The common fix for cyano is adding another bacterial type that targets and consumes the carbon available in the tank, so it can be filtered or skimmed out. And ofcourse we use GFO or Lanthanum Chloride to bind up phosphates that we then remove out of the system.

The temptation is often to INCREASE feedings to increase NO3 or PO4, but that increases Nitrogen and Phosphorous and Carbon , but in reality, you just have to REDUCE any free Carbon in your tank to see NO3 and PO4 rise. that's why many reefers use products like Dr Tims / Zeovit supplements etc, to control the carbon in the tank, which in turn stops the Algae AND Cyano issues, allows higher maintainable NO3/PO4 for coral growth/colour, as well as good husbandry to keep a "clean" system.

Personally, I would keep your refugium about half full of chaeto, leaving it room to grow. Feed less. Keep everything clean. only use GFO if needed. Skim 24/7.

With your NO3 of 5ppm and PO4 of 0.05ppm, you have 3 choices....

1. carbon dose to get your NO3 to equal 16 x 0.05ppm PO4 = 0.8ppm NO3
2. reduce / stop GFO use until PO4 = 5ppm NO3 / 16 = 0.31ppm PO4
3. if you reduce the free carbon in your tank as well, you should be able to make the carbon the limiting factor, so that you can hold your NO3 / PO4 at any desired levels, without having algae / cyano issues.

Having slightly too high NO3 is always better than too high PO4. Excessive PO4 browns out corals and slows growth.

Also, test kits (and us humans) are fairly in accurate, don't chase exact numbers too hard.... they are a guide to what we can reliably test / dose for.

There is another factor in coral coloration, and that is trace elements.... I have found that dosing the red sea colours ABCD greatly improves my coral colors, but KZ do a great range too.

This is great! Exactly what I was hoping to learn. Thanks.

 

[Randy Holmes-Farley]

This is great! Exactly what I was hoping to learn. Thanks.

I disagree strongly.

 

[Randy Holmes-Farley]

The Redfield ratio is NOT a target level in the tank, nor should it be considered so. It is the uptake ratio. Those are two totally different things.

By that thinking, if calcium is 420 ppm, alkalinity should be 65 dKH because that is the uptake ratio that corals use in calcification.

 

[LV3]

@Randy Holmes-Farley I clearly need to educate myself more on both topics (Redfield and uptake ratio) to better understand the differences. I'm fairly new to reef keeping and the information I've consumed regarding parameters has always been somewhat consistent. For instance, PO4 = .03, 8-9dKH, Ca 420-440, Mg 1380-1400, Nitrates (up to this point, near zero), etc.. What I find interesting are the ways systems can be maintained at different levels given specific conditions. I've seen some tanks online running well over 40ppm of Nitrate and wonder how they do it which is what prompted me to start thinking about the relationship of elements and their affect in the tank.

 

[Randy Holmes-Farley]

Yes, there are many ways to run a great reef tank. I think that unless you are going for the pastel look of a ULNS tank, most folks find things work pretty well at about 0.01-0.03 ppm phosphate and a few ppm of nitrate. Outside those ranges can still be OK, but often other factors become more important (such as a different way to keep algae in check if N and P are higher).

If you want fastest coral growth, you can push alk up to the higher end of normal (say, 9-12 dKH), but be sure to have adequate N and P or you may get burnt tips, possibly from skeletal growth proceeding faster than tissue growth can keep up.

 

[LV3]

So is it sounds like and I've heard that it's difficult to have both accelerated growth and vibrant coloration. If that's true, could a tank run a higher alk/N & P for a period of time to grow out and then switch to a lower alk/N&P to then bring in the color? My concern in that approach would be the swing in alk unless of course it was reduced slightly over a month or so. Thoughts?

 

[Randy Holmes-Farley]

So is it sounds like and I've heard that it's difficult to have both accelerated growth and vibrant coloration. If that's true, could a tank run a higher alk/N & P for a period of time to grow out and then switch to a lower alk/N&P to then bring in the color? My concern in that approach would be the swing in alk unless of course it was reduced slightly over a month or so. Thoughts?

Probably yes. Higher nutrients to allow faster growth may result in browner corals due to higher zooxanthellae levels (and possibly other reasons), but that can be changed by changing the conditions later.

 

[rushbattle]

The Redfield ratio is NOT a target level in the tank, nor should it be considered so. It is the uptake ratio. Those are two totally different things.

By that thinking, if calcium is 420 ppm, alkalinity should be 65 dKH because that is the uptake ratio that corals use in calcification.

Randy, you have been making this point for many years in many different instances. I struggle to understand how so many people have misunderstood the concepts so thoroughly, yet are so adamant about spreading these misleading (at best!) concepts so fervently. Your example is a perfect illustration of how wrong/misleading it can be. Imagine if folks aimed for 65dkh!!!

I guess this is a strange way to say thank you. I aplaud your diligence over the years and your immense patience with those less familiar with science and all of its basic principles as it applies to reefkeeping. Not to mention the misconceptions surrounding reefkeeping and chemistry. You have been helping us with so much for so long.

I was going to PM this whole message, but I guess I wanted to share my gratitude for your efforts publicly. I know it's unlikely that you would accept a donation for your efforts, but perhaps you could let us know, or PM me singly, with a way to donate to something you care about and believe in. Thanks again for all of your hard work!

 

[Rob Lion]

The Redfield ratio is NOT a target level in the tank, nor should it be considered so. It is the uptake ratio. Those are two totally different things.

By that thinking, if calcium is 420 ppm, alkalinity should be 65 dKH because that is the uptake ratio that corals use in calcification.

At no point did I ever suggest that calcification followed redfield I see no reason why you felt the need to make that remark.

Life in sea water is a balance.... and mother nature balances the N : P ratio very close to the redfield ratio. Whilst we can maintain whatever N : P ratios we wish in a reef tank, issues can soon arise whenever they are strayed from, which is why in answering the OP's question

if anyone can explain the relationship between PO4 and NO3 in the system I think that would be helpful for me.

I added the common issues found and why.

Here is an abstract from

Redfield revisited: 1. Regulation of nitrate, phosphate, and oxygen in the ocean
Authors

• Timothy M. Lenton,
• Andrew J. Watson

Abstract
The ratio of phosphate and nitrate concentrations in the deep ocean matches closely the Redfield ratio required by phytoplankton growing in the surface ocean. Furthermore, the oxygen available from dissolution in ocean water is, on average, just sufficient for the respiration of the resulting organic matter. We review various feedback mechanisms that have been proposed to account for these remarkable correspondences and construct a model to test their effectiveness. The model's initial steady state is close to the Redfield ratios and stable against instantaneous changes in the sizes of the nitrate and phosphate reservoirs. When classic flux estimates are adopted, nitrate responds to perturbation in 1000-2000 years and phosphate in 40,000-60,000 years. However, recently increased estimates of the input and output fluxes of nitrate and phosphate suggest that they respond more rapidly to perturbation, nitrate in 500-1000 years and phosphate in 10,000-15,000 years. Nitrogen fixation tends to maintain nitrate close to Redfield ratio with phosphate, while denitrification tends to keep nitrate as the proximate limiting nutrient and tie it in Redfield ratio to dissolved oxygen. Under increases in phosphorus input to the ocean, the relative responsiveness of nitrogen fixation and denitrification determine whether nitrate remains close to Redfield ratio to phosphate or to oxygen. If nitrogen fixation is strongly limited (e.g., by lack of iron), increasing phosphorus input to the ocean can cause phosphate to deviate above Redfield ratio to nitrate. Hence nitrogen dynamics can control phosphate behavior and nitrate can potentially be the ultimate limiting nutrient over geologic periods of time. When nitrate and phosphate are coupled together by responsive nitrogen fixation, negative feedbacks on organic and calcium-bound phosphorus burial stabilize their concentrations. If anoxia suppresses organic phosphorus burial, the resulting feedbacks on phosphate (positive) and oxygen (negative) improve regulation toward the Redfield ratios. Variants of the model are forced with a global record of phosphorus accumulation in biogenic sediments as a proxy for changes in phosphate input to the ocean over the past 40 Myr. Nitrate is generally regulated close to Redfield ratio to phosphate, despite large changes in phosphorus input. If nitrogen fixation is strongly limited, then there is one interval (similar to 15 Myr ago) when a very rapid increase in phosphate input forces phosphate above Redfield ratio to nitrate. Decreases in phosphorus input cause phosphate and nitrate to quickly deviate below Redfield ratio with oxygen, removing anoxia from the ocean, while increases in phosphorus input rapidly increase anoxia. Hence we conclude that there appears to be an element of chance in observing today's ocean "on the edge of anoxia" with nitrate, phosphate, and oxygen all close to the Redfield ratios.

--------------------------------------------------------------------------------------------------------------------------------------------------------
If mother nature follows this ratio, I see no reason why this ratio shouldn't be also suitable for our reef tanks, with the exception that in our small water worlds we create, the levels of N and P should be higher as we don't have the continuous water changes the oceans have that stops limitation of the much needed ions.

 

[Randy Holmes-Farley]

At no point did I ever suggest that calcification followed redfield I see no reason why you felt the need to make that remark.
.

Because it is a perfect analogy that shows the Redfield ratio (an uptake ratio, which is EXACTLY analogous to the uptake ratio of 18-20 ppm calcium for each 2.8 dKH of alkalinity) is NOT an aquarium target ratio and should not, buy itself, be used as such.. It is simply the ratio of elements that the organism uses.

The fact that, in the article that you post, some parts of the ocean (not the part where our organisms live, by the way), happens to fall at ONE point on this ratio is meaningless (IMO). To say the ratio is desirable at any other point is just not right, as my extreme examples point out. If you want to quote concentrations in tropical ocean surface waters and give those as targets, that makes much more sense, but itself has limitations since we do not feed corals the same as they are fed in the ocean.

Do you really think that if nitrate is 500 ppm, that the "optimal" phosphate level is several ppm?

That said, let's look at why the deep oceans might follow the Redfield ratio. It is not because photosynthetic organisms are adapted to uptake from this ratio, it is because the dead phytoplankton sinks to the deep ocean, degrades, and releases these nutrients in the ratio that comprises their bodies. They are supplying the nutrients in the ratio they already have.

In surface waters, where our corals and such thrive, the concentrations are very different, and both are typically much, much lower than the deep ocean because they are being scavenged like mad by photosynthetic organisms (unless we are talking about polluted water near human habitation, or one of those few locations where there is significant upwelling of deep water).

So the point is, is the ratio of nitrate to phosphate important, or is it the amount of each that is importnat?

There's no evidence that the ratio is important per se that I have ever seen. The evidence suggests that both too low but in the "right" ratio is a problem and both too high but in the "right" ratio is a problem.

Here's a paper, for example, where they discuss both elements rising together and they discuss how having the nutrients cross threshold levels (that is, they are no longer limiting to algae growth) is what causes algae problems in the ocean:

https://www.researchgate.net/profil...al-reefs-in-Jamaica-and-southeast-Florida.pdf