Should I dose nitrate/PO4?

[Randy Holmes-Farley Verified Community Expert]

Randy sometimes logic doesn’t match reality for whatever reason. Have you dosed TSP in your own system and compared to other PO4 products?

No, but I've also not tried to breathe in high vacuum. In both cases, I know what will happen.

 

[Randy Holmes-Farley Verified Community Expert]

Hehe…wait a minute….you said there was no difference! Identical remember.

Please show me, if true, and I'll fix it. I think I have been careful and clear in what I wrote, but perhaps something slipped by. I have stated MANY times in posts to you this sort of comment, and I stand by it 100%:

"I’ll just reiterate that I do not think that the form of phosphate dosed will matter to any reef tank, and if there are differences that are reproducible, the effect must be from undesirable impurities in some materials."

The thing that is identical is the phosphate once dissolved. There is NO bioavailability difference or toxicity difference.

The tiny pH and alk efffect, and a small difference in sodium added (against a background of sodium that is more than a hundred thousand times higher) are the only differences.

How big is that effect? Let's see. I think you might be surprised that I even mention it, but in the spirit of being 100% accurate, I do mention it.

Let's suppose that we add a large amount, 0.1 ppm phosphate via trisodium phosphate. We can assume that most of the phosphate added to the aquarium picks up one proton to form HPO4- (the predominate form at pH 5.9 to 8.75 in seawater)

PO4--- + H+ ---> HPO4--

0.1 ppm phosphate ~ 0.1 mg/L

phosphate molecular weight is 95 grams per mole or 95 mg/millimole

0.1 mg is thus 0.0011 millimoles

0.1 mg/L = 0.0011 millimole/L

Thus, we add 0.0011 meq/L = 0.0031 dKH

I did an experiment where I showed that removing 0.5 meq/L (1.4 dKH alk equivalent) of H+ raised pH by 0.066 pH units in seawater. Thus, removing 0.0011 meq/L of H+ will boost pH by roughly 0.0011/0.5 x 0.66 = 0.0014 pH units.

So we see the expected effect of using trisodium phosphate to add 0.1 ppm phosphate:

A boost of alk by 0.003 dKH
A boost of pH by 0.0014 pH units

You will not be able to detect those changes and is why I consider them to be irrelevant, despite the fact that i do note they exist.

 

[Randy Holmes-Farley Verified Community Expert]

I highly doubt that Randy. You’re a Chemist and I have much respect for you,
but with all due respect, what you’re saying doesn’t not line up with the effects I’ve seen in my own tank. I’ve tested multiple PO4 products on the market and I find TSP to be the absolute worst of all. I have the data that proves it. I’m not the only reefer that has experienced this either.

Nonsense. That is a gross misunderstanding of what I have said, and of chemical reality.

If you saw an effect, and if others did, it could certainly be for reasons such as possible impurities or inappropriate dosing amounts. I do not recall you posting exactly what you used and how much, but maybe you did.

There's no need to think that some weird effect unknown to man has emerged from your use of a simple phosphate salt when there are obvious and straightforward explanations at hand.

 

[Randy Holmes-Farley Verified Community Expert]

I don’t know that it is, but I do know TSP is horrible for my tank and corals. That’s a fact. When I stopped it and transitioned to another product it was like somebody flipped a light switch. Within a week there was a marked difference in color, water clarity, algae growth, and the PO4 level start to come up.

Currently I’m testing Potassium Phosphate Dibasic and seeing much better effect vs TSP. However, I never want to elevate the Potassium level if I can help it, but will be looking at the next ICP to see how much it’s elevated if any at all. If it’s minimal I can deal with that. If it’s a lot, I’ll change over to Sodium Phosphate Monobasic and start testing that one.

The potassium effect is real, but very small since so little phosphate is dosed. It's a far smaller concern than for potassium nitrate dosing.

 

[KStatefan]

I don’t know that it is, but I do know TSP is horrible for my tank and corals. That’s a fact. When I stopped it and transitioned to another product it was like somebody flipped a light switch. Within a week there was a marked difference in color, water clarity, algae growth, and the PO4 level start to come up.

Currently I’m testing Potassium Phosphate Dibasic and seeing much better effect vs TSP. However, I never want to elevate the Potassium level if I can help it, but will be looking at the next ICP to see how much it’s elevated if any at all. If it’s minimal I can deal with that. If it’s a lot, I’ll change over to Sodium Phosphate Monobasic and start testing that one.

How are you determining what is good or bad in your test?


Potassium Phosphate Dibasic is 55% Potassium so if you are adding 0.05 ppm per day of phosphate you will be adding 0.04 ppm of Potassium so at the end of a year your phosphate will raise 14.6 ppm without doing anything to remove like water changes. Not much of a change to 400 ppm NSW

Updated math

 

[Reefahholic]

Please show me, if true, and I'll fix it. I think I have been careful and clear in what I wrote, but perhaps something slipped by. I have stated MANY times in posts to you this sort of comment, and I stand by it 100%:

"I’ll just reiterate that I do not think that the form of phosphate dosed will matter to any reef tank, and if there are differences that are reproducible, the effect must be from undesirable impurities in some materials."

The thing that is identical is the phosphate once dissolved. There is NO bioavailability difference or toxicity difference.

The tiny pH and alk efffect, and a small difference in sodium added (against a background of sodium that is more than a hundred thousand times higher) are the only differences.

How big is that effect? Let's see. I think you might be surprised that I even mention it, but in the spirit of being 100% accurate, I do mention it.

Let's suppose that we add a large amount, 0.1 ppm phosphate via trisodium phosphate. We can assume that most of the phosphate added to the aquarium picks up one proton to form HPO4- (the predominate form at pH 5.9 to 8.75 in seawater)

PO4--- + H+ ---> HPO4--

0.1 ppm phosphate ~ 0.1 mg/L

phosphate molecular weight is 95 grams per mole or 95 mg/millimole

0.1 mg is thus 0.0011 millimoles

0.1 mg/L = 0.0011 millimole/L

Thus, we add 0.0011 meq/L = 0.0031 dKH

I did an experiment where I showed that removing 0.5 meq/L (1.4 dKH alk equivalent) of H+ raised pH by 0.066 pH units in seawater. Thus, removing 0.0011 meq/L of H+ will boost pH by roughly 0.0011/0.5 x 0.66 = 0.0014 pH units.

So we see the expected effect of using trisodium phosphate to add 0.1 ppm phosphate:

A boost of alk by 0.003 dKH
A boost of pH by 0.0014 pH units

You will not be able to detect those changes and is why I consider them to be irrelevant, despite the fact that i do note they exist.

Chemist activated! Haha

 

[Reefahholic]

Nonsense. That is a gross misunderstanding of what I have said, and of chemical reality.

If you saw an effect, and if others did, it could certainly be for reasons such as possible impurities or inappropriate dosing amounts. I do not recall you posting exactly what you used and how much, but maybe you did.

There's no need to think that some weird effect unknown to man has emerged from your use of a simple phosphate salt when there are obvious and straightforward explanations at hand.

Let us compare by pictures.

First let’s observe the effect of TSP dosing. Never once did I see any hint of green in the tank. Nothing on the glass and nothing on the overflow, rocks, or sand. When I passed the algae scrapper it felt like it was having trouble sliding on the glass. Almost like it was too clean. Like rubbing instead of sliding. I kept dosing up intentionally to try and saturate the tank or get decent readings. For months I couldn’t get it much above zero and that was dosing up to 0.16 ppm daily. The rocks turned almost black, but the PO4 level remained depleted on the Hanna Phosphorus ULR checker and also on ATI analysis. Basically zero or extremely low every test. Lost 2 Acro’s despite feeding Spirulina and other coral Nutrition. The Vivid Confetti and Millie that RTN’ed had green skeletons, because they up took the food, but the PO4 was so low they couldn’t survive. The TSP wasn’t bioavailable “enough” and the effect on the tank matched up exactly to what they say it’s used for. It was a cleaner type effect for sure.

“TSP is used as a cleaning agent, builder, lubricant, food additive, stain remover, and degreaser.” - Wikipedia

Now let’s look at when I switched away from TSP. I was FINALLY able to grow some algae and get the much needed PO4 in the tank and the levels started to come up. The tangs started to graze the rocks, the cloudy water cleared up, corals almost instantly colored up, and the tank took a hard turn for the better. Remember, for months I was dosing TSP at 0.16 ppm and none of this ever happened. I was finally able to reduce the dose. The corals started getting increased PE and stared to grow. NOTE THE BACK GLASS IN BOTH PICS.

 

[Reefahholic]

The potassium effect is real, but very small since so little phosphate is dosed. It's a far smaller concern than for potassium nitrate dosing.

I can report back on that. Just received my analysis right before I started. I’m dosing quite a bit of PO4 currently so we’ll see how high it’s elevated if any at all. Of course every system is different, but at least we’ll see what happens in a about 3 weeks. If it does elevate quite a bit, I’m going to switch to Sodium Phosphate Monobasic.


Quick question…I noticed when you were looking at the molecular weight for TSP to convert the difference from Potassium Phosphate on the calculator. You used the percentage of TSP instead of g/mol.

How do you calculate the percentage of TSP from g/mol.?

I know it’s 163.94 g/mol or you said 58% Phosphate by weight. I’m guessing it weighs more than the Postassium Phosphate which is why we multiply the product to add by 0.77 to reduce it by about 23%.??

 

[Reefahholic]

How are you determining what is good or bad in your test?

By the way the tank responds. I do realize this tank is much different from most and from all my tanks in the past, but this makes testing that much easier to observe how well a product works. It’s hard to determine on a tank that is already saturated. With a starving tank results are noted quickly, because the corals are barely surviving.

To further answer your question I’m looking for things like PE, Color, PO4 level, water clarity, algae, etc.

 

[KStatefan]

Quick question…I noticed when you were looking at the molecular weight for TSP to convert the difference from Potassium Phosphate on the calculator. You used the percentage of TSP instead of g/mol.

How do you calculate the percentage of TSP from g/mol.?

I know it’s 163.94 g/mol or you said 58% Phosphate by weight. I’m guessing it weighs more than the Postassium Phosphate which is why we multiply the product to add by 0.77 to reduce it by about 23%.??

 

[Reefahholic]

According to that, it should be a 13-14% reduction. So why have we been multiplying by 0.77? What am I missing?

 

[Reefahholic]

Where do they get the weight percentage from? None of the numbers add up to those percentages.

 

[Randy Holmes-Farley Verified Community Expert]

You seem focussed on other uses of tsp, as if that indicates why it’s a problem. Let’s look deeper at WHY it is used in cleaners.

It is used in cleaners for two reasons, and no other reasons.

1. It raises pH. At high pH, fats are hydrolyzed to soaps. That’s the slippery feel when a high pH solution gets on your skin. This effect makes all high pH solutions capable of dissolving fat/grease/etc. and other materials that are soluble at high pH

2. The phosphate precipitates ions that interfere with soaps, such as calcium and magnesium. Hardness ions.

Thus, there is no “cleaning effect” in a seawater aquarium dosing 0.1 ppm phosphate. I showed above that the pH effect is too small to measure, and even if some precipitation happens, it too is too way too small to detect even if every single phosphate ion added precipitated (much less than a 0.1 ppm calcium loss).

 

[Randy Holmes-Farley Verified Community Expert]

According to that, it should be a 13-14% reduction. So why have we been multiplying by 0.77? What am I missing?

The spreadsheet is comparing Na3PO4 to K2HPO4.

The ratio of molecular weight of Na3PO4 to K3PO4 is 0.77.

 

[KStatefan]

Where do they get the weight percentage from? None of the numbers add up to those percentages.

What does not add up? I could have a mistake in there.

I did have a mistake forgot to change a formula after copy and paste

I entered Potassium Phosphate Dibasic into my spreadshhet since that is what you said you were currently testing.

 

[Reefahholic]

Thus, there is no “cleaning effect” in a seawater aquarium dosing 0.1 ppm phosphate.

Well, I maybe people should try it. It’s probably ok for a saturated tank and small volume dosing. For higher demand tanks you can clearly see from the pic comparison that the other product was far superior. Ultimately, I was able to get some much needed PO4 into the system that the corals could uptake. They colored up within a week. PE was much better. PO4 finally started increasing on both the Hanna Phosphorus ULR and ICP. ALK demand went up. I was able to appreciate a light green haze on the front and back glass (what a wonderful site) as seen in the picture. Water clarity improved due to the increase in PO4 from depleted levels (also observed in the pic). I never saw anything like that from Trisodium Phosphate even after dosing very high volumes for months. A friend of mine experienced the exact same. A few other guys too.

It’s obvious not all Phosphate products are created equally. From what I’ve seen and experienced form dosing TSP “heavily” for 2-3 years, it will never be a choice for me. I don’t care how close (in form) it may appear to be with the other products I listed in this thread. Ain’t Comin’ in my reef.

 

[Randy Holmes-Farley Verified Community Expert]

It’s obvious not all Phosphate products are created equally. From what I’ve seen and experienced form dosing TSP “heavily” for 2-3 years, it will never be a choice for me. I don’t care how close (in form) it may appear to be with the other products I listed in this thread. Ain’t Comin’ in my reef.

I'll again reiterate that, IMO, if you see an effect that is different, it is due to impurity differences.

No matter what you observed, why do you not acknowledge that is a possibility that makes chemical sense while other hypotheses seems hard to swallow?

 

[Reefahholic]

I'll again reiterate that, IMO, if you see an effect that is different, it is due to impurity differences.

No matter what you observed, why do you not acknowledge that is a possibility that makes chemical sense while other hypotheses seems hard to swallow?

It does make sense. I will acknowledge that. It’s possible. I just don’t think that’s the culprit. Hehe

I do want to thank everybody for participating in this conversation and giving their input and feedback. We all have different opinions and that’s good! Like I said, I will continue to test a lot of these products and report the observations.

 

[Reefahholic]

You never told me how to calculate weight Randy.

What is the formula for g/mol to percentages.?! I need to be able to calculate the differences in molecular weight. Currently using a coral farmer’s Excel program that’s very accurate. Tired of bugging him. Lol

 

[KStatefan]

You never told me how to calculate weight Randy.

What is the formula for g/mol to percentages.?! I need to be able to calculate the differences in molecular weight. Currently using a coral farmer’s Excel program that’s very accurate. Tired of bugging him. Lol

What weight are you trying to calculate?

This is my calculations for Sodium Phosphate Dibasic there is not much math behind the spreadsheet just multiply the atomic weight by the number of atoms to get total weight of each element then sum those. Then divide the weight of each element by the total to get the percentage of each. Add the oxygen and phosphorus together to get the phosphate %