A Nitrate Dosing Calculator For Better Tank Health (And Better Coral Color!)

by Stratos

It has become a phenomenon of increasing frequency in the reefing hobby today to have “too clean” of a tank.  Zero nitrates, and sometimes even zero phosphates are found behind more and more tank issues.  Either can be quite problematic for the tank.

With the ever popular “ULNS” systems and all methods of carbon dosing exponentially increasing in usage, nutrient starvation in our glass boxes is almost as common as the opposite.  Pale colors in corals are one of the more common side effects.  But there can be many side effects to a tank’s microbial food web ,aka microbial loop.  (Also see other entries in the Nutrients section of the blog.  –Ed)

Thankfully, there are many ways to increase and maintain nutrients.

Limiting nutrient export (e.g. water changes, reduced skimmer usage, shorter refugium lighting hours, etc) and increasing the rate of nutrients introduced into the system with extra feedings might be the two easiest ways.

However, in some cases, “nutrient dosing” is definitely something of interest – particularly nitrate dosing.

There has been a lot of discussion about the different reagents that could be used – a great one being potassium nitrate (KNO3).  Also known as salt peter.

One great source for KNO3 is a product by Spectracide called Spectracide® Stump Remover Granules.

Initially this registered on my radar from an excellent post on Reef2Reef.

I was intrigued by the idea of being able to add exactly what the system needs.

The instructions on the thread are fairly easy and straightforward:

  • Add 2 tablespoons of the Sump Remover (granules) in a plastic cup of RODI water.
  • Use that to dose approximately one milliliter per ten gallons of aquarium water.
  • Then test and adjust accordingly.

Although this is a very simple approach, I had an uneasy feeling which kept me from slapping a quick dilution together and dumping it in. I wanted to have some additional confidence that it would succeed and perform as expected.  Knowing that I can easily calculate the exact dilution to raise nitrate exactly, I started digging a little further.

My first data was the SDS (Safety Data Sheet) of the Spectracide product.  It states unequivocally that the composition is 100% potassium nitrate. This is a bold statement to make as many SDS like to leave room for impurities – anything up to 99% potassium nitrate would have left the door open for some impurity. 100% purity gives a good comfort in using the product and expecting it to be and perform as predicted.

KNO3 Screen.pngIdeally, for my purposes, a calculator is created to assist with the dosing.

The calculator I created (depicted to the left)  consists of three main parts.

The first part helps with the creation of a stock solution that has a known nitrate content.

The second part helps with determining how much of that stock should be added in a known volume (your tank’s volume) to increase nitrate by how much.

The third section is where specific doses are calculated to address specific deficiencies.

The calculator is assembled as a Google docs sheet here.

Look closer at the KNO3 molecule in the Molecular Properties section of the calculator.

In order to know how much nitrate we will be adding, we need to know what is the ratio of nitrate is to other atoms in the KNO3 molecule by mass. 

That section concludes that the ratio is about .61.  Or in other words, about 61% of the weight of the KNO3 molecule is nitrate.

Solution Properties, the second section of the table, shows that if we create a stock solution of 10 grams of KNO3 in 500 milliliters of RODI water we are going to have a solution that has approximately 12,265 ppm of nitrate.

The third block, Dosing Calculations, shows that if we take 1 milliliter of the stock solution and we dose it into a 30 gallon system, we are going to increase nitrate by 0.1 ppm.

Indeed, following this, I created the depicted solution and dosed 5 milliliters in my 30 gallon tank and after an hour, when I tested, I had 0.5 ppm of nitrate.

It’s worth noting that to help keep the integrity of the calculations, the sheet is shared as “view only”.

You can still make a copy of it on your drive or if you don’t have a Google account you can also download the file to your computer.

In that calculator, there are a couple more things worth mentioning.

First, the other different forms of nitrate available also have calculators built into the Full tab of the spreadsheet – namely sodium nitrate and calcium nitrate each have their own calculator table.

It is fairly straight forward to make a similar table for any salt like those just by looking at the molecule and determining the nitrate ratio. For instance, the calcium nitrate molecule has two nitrates for one calcium. That has to be taken into account when calculating as this relationship makes it “nitrate heavy”.  This methodology can be used for other compounds as well. Another good example checmical is potassium chloride for dosing potassium in the tank, but without affecting nitrates. The idea is the same within the calculator.

Secondly, there is also a tab called Simple which allows for a quick and dirty calculation resembling the ones everyone is used to from the venerable Reef Chemisty Calculator, and others.

The Simple View tab answers the question “how many grams of potassium nitrate to add to the tank to increase by how many ppm”. This foregoes the middle step of creating a stock solution and dosing that one which might be useful when dosing with a pump.

All things considered, any method of adding it can work. If you want something simple, then just putting the recipe together from the post on Reef2Reef might be all you need. If you want to achieve more control, the calculator might be more your style.

Either way, keep your corals fed!

The in situ light microenvironment of corals

The in situ light microenvironment of corals

Daniel Wangpraseurt, Lubos Polerecky, Anthony W. D. Larkum, Peter J. Ralph, Daniel A. Nielsen, Mathieu Pernice and Michael Kühl
Limnol. Oceanogr., 59(3), 2014, 917-926 | DOI: 10.4319/lo.2014.59.3.0917

Full article available!

I don’t understand the choice of words “Scalar irradiance”, but themeaning in my words, is the total irradiance from every angle.  Sunlight from “up”, light from reflections off the sand, off the coral’s own skeleton, et al.

The typical light measurement you’ll see on a hobby website using a PAR or lux meter is what this paper would be called a measurement of “downwelling irradiance”.

(Measurements of light in air don’t seem to have so many complications or aspects.)

Light is strongly scattered at the water–tissue interface and within the coral tissue, where photon trapping and redistribution leads to significant enhancement in the local scalar irradiance compared with the incident downwelling irradiance (Ku ̈hl et al. 1995; Wangpraseurt et al. 2012a).

Additionally, reflective, fluorescent, or both host pigments are synthesized by many corals, which further alters the intensity and spectral quality of light due to, for example, intense scattering and red-shifted emission (Salih et al. 2000).

Finally, photons that pass through the tissue are backscattered by the aragonite skeleton, further enhancing tissue scalar irradiance and thus photon availability for zooxanthellae photosynthesis (Enriquez et al. 2005; Marcelino et al. 2013).

Spectral scalar irradiance at the upper surfaces of faviid corals (E0) differed markedly from the incident downwelling irradiance (Ed; Fig. 3). Depending on the wavelength in the PAR region, the E0 : Ed ratio varied between 0.8 and 2.4, with the most pronounced enhance- ment at wavelengths 500–640 nm and . 680 nm (Fig. 3a–c).

[Ed:  500-640 nm is green of plant and human-color-vision “fame”, and 680nm is far-red like the light emitted from chlorophyll.]

it will be useful to compare differences between coenosarc and polyp tissue because they differ in total light exposure and spectral quality (Figs. 3, 4; Wangpraseurt et al. 2012a) and can exhibit different patterns of photoacclimation (Ralph et al. 2002).

There’s much more in there too!

They don’t go into this angle, but I think either all of, or a significant portion of, this “scalar light” other than the incident downwelling is actually “waste light”from the coral “blowing off” excess photons during photo-saturation.

Makes sense as green light isn’t well-absorbed and red light is low-function in the photosynthesis cycle.

Quoting http://plantphys.info/plant_physiology/light.shtml:

“Light beyond 700nm has insufficient quantum yeild to drive photosynthesis.”

680nm may as well be 700nm as far as this goes….”mission accomplished” in modern parlance.

The photons have had their “kick” removed in the red cases, or they’ve been made ultra-reflective in the green cases.

Seemingly contradictory to the above  (and also mentioned at that link) is the Emerson effect, where chlorophyll can use 680nm + 700nm light to significantly boost photosynthesis.

Very interesting!

Kill A Watt Power Meter

20160125-110540.jpgI use this Kill A Watt meter to measure any device I have electricity questions about.  I also use it to measure total system power usage and even to track cost over time.

For the price, a Kill A Watt meter eliminates so many questions and has even given me some answers I didn’t know the questions to yet!

Highly worth the cost!

“Full Spectrum” – The Internet Reefer’s Decoder Ring

Full Spectrum

Visble Light Spectrum
Visible Sunlight (Credit: NSO/AURA/NSF)

By Matt Carroll

Before we even talk about the term “full spectrum“, please take a moment to enjoy the above high resolution spectrograph of “white light” from the sun, courtesy of the folks at NOAO.

(They offer even higher resolution versions at the link.   They also offer a hi-res spectrograph of the sun’s entire spectrum – white light, plus everything else.)

Note the numerous gaps as we get on with the discussion!


The original electric light was an incandescent light bulb.

Incandescent bulbs produce a full spectrum light not unlike the spectrum of white light put out by the sun at a certain time of the day.

In contrast to these old-style lights, electric lights we are familiar with in the hobby such as fluorescent lamps and high intensity discharge (HID) metal halide lamps all put out nearly monochromatic light mostly based on the emission of mercury vapor at various combinations of pressure and temperature.  Although sodium lights are another monochromatic alternative.220px-hg-spektrum_crop

Here’s an example spectrum of mercury’s color emission from Wikipedia:

Not full spectrum at all.  To the eye it’s more of an ugly green light with very few wavelengths of light present.

Let’s look at more examples!


imageHere’s a sample of the output from my spectrometer with the spectrum provided by a GE Reveal incandescent bulb.

This is a bulb with a bluish neodymium coating that causes the spectrum to be choppier than a regular clear glass incandescent bulb.  That is the reason for the few dim spots in the spectrum.


Most cheap, household fluorescents aren’t that far removed from the basic mercury emission, which you will recall only puts out a few  spikes of color in red green and blue.

imageHere’s a sample of the output from my spectrometer with the spectrum provided by an Ikea branded 11-watt compact florescent (CFL) bulb:

spectrometer_outputNext is a great example of a Phillips florescent bulb that has been heavily modified to be “full spectrum”:

From comparing those two photos, it’s clear what folks meant when they came up with the term “full spectrum”.

It meant not missing 90% of the color spectrum. Pretty sensible.

(Interestingly, you can still see the mercury emission lines standing out among the rest of the spectrum generated.)


In reefing, “full spectrum” is a different thing altogether.  A “full spectrum” LED light does not restore 90% of the color missing from ordinary white LED’s, for example.  In fact, the term doesn’t really have any inherent color meaning.

Instead, it is used as a term to contrast with either the light given off by ordinary “white light” LEDs or a basic blend of blue and white light LEDs.

The problem with this is that white LED’s are already very full spectrum – there are merely a few weak wavelengths below the greens and above the blues.

img_3237Here’s a sample of the output from my spectrometer with the spectrum provided by a generic 6500K “white” LED bulb:

Unlike the CFL picture above, this looks “full spectrum”.  Very similar to the incandescent photos.  If you have good eyesight or look hard, you can see the dim spot in the spectrum.  It is real, but it’s barely there.

Confusingly, in practice, “full spectrum” reef lights do nothing about missing wavelengths.

What they do, generally speaking, is start with a solid, blue+white LED “reef blend” and add RGB (red, green and blue) LED’s so folks can add a decorator effect where one or more of the colors is exaggerated.

How added RGB is supposed to translate into filling that little blue-green wavelength gap in the photo – and why “full spectrum” is the marketing term they chose to use – is anyone’s guess.

(And please don’t tell anyone about the holes in the spectrum of sunlight or it’ll be deemed not full spectrum too!)

Stay tuned to the Internet Reefer’s Decoder Ring series for more!

Entries in the Internet Reefer’s Decoder Ring are terms you’ll find in the course of online discussion about reefing that make very little sense. In some cases, these terms seem to have been borrowed from another industry where the term did have meaning, but the meaning did not carry over to reefing.