Nutrients to ALK Ratio?

[Bear22]

Guys,

My alkalinity seems to be on autopilot at around 9.5dKH with pH usually between 8.2 to 8.4. I'm already using a "low" alkalinity salt mix with TM Pro. I do a weekly water change.

At these levels what NO3 level might be a good target to shoot for? Does PO4 need to be tweaked as well?

TIA

 

[Dread Pirate Dave]

Guys,

My alkalinity seems to be on autopilot at around 9.5dKH with pH usually between 8.2 to 8.4. I'm already using a "low" alkalinity salt mix with TM Pro. I do a weekly water change.

At these levels what NO3 level might be a good target to shoot for? Does PO4 need to be tweaked as well?

TIA

Following. I didn't think there was a real relationship between these.

 

[BeanAnimal]

Just keep both in a reasonable range.

https://www.reef2reef.com/ams/randy’s-thoughts-on-nutrient-target-ranges.1087/

 

[exnisstech]

The only thing I've heard can be bad is low nutrients with high alk. Have no idea of ratios. I've never thought of trying to keep N and P at a certain level related to alk.

 

[Poseidon03]

I've always had more success by focusing more on stability in the right range rather than a ratio. Nitrate 10-20ppm phosphate .08-.12. If the test is outside this range, I'll try to slowly correct over the next month.

 

[Randy Holmes-Farley Verified Community Expert]

The only relationship that I am aware of is that if alk (and pH) are high, nutrients should not be too low or there is a risk of burnt tips on some SPS.

One hypothesis is that the skeleton grows faster than tissue can keep up if nutrients are too low.

 

[JonasRoman]

Guys,

My alkalinity seems to be on autopilot at around 9.5dKH with pH usually between 8.2 to 8.4. I'm already using a "low" alkalinity salt mix with TM Pro. I do a weekly water change.

At these levels what NO3 level might be a good target to shoot for? Does PO4 need to be tweaked as well?

TIA

Hi. Nutrients are not connected to alkalinity. Its separate parameters and questions. But one thing to mention, if you have very high alkalinity, that can be stressfull to corals, and such a stress corals stands less if also the nutrients (especially PO4) are very low, like below 0.02.

Alk shall be IMO close to NSW, thus around 7-8 dKH.

Nutrients (thats has nothing to do with alk), is another and huge question, where my opinion is that PO4 should never go below 0.02 as low PO4 is dangerous, but low NO3 is not dangerous, but rather bad if going to high in long term. So my ideal values are (my personal opinion):
KH:7-8 dKH
NO3:0-5 mg/l
PO4: 0.04-0.1 mg/l

Jonas

 

[Bear22]

Hi. Nutrients are not connected to alkalinity. Its separate parameters and questions. But one thing to mention, if you have very high alkalinity, that can be stressfull to corals, and such a stress corals stands less if also the nutrients (especially PO4) are very low, like below 0.02.

Alk shall be IMO close to NSW, thus around 7-8 dKH.

Nutrients (thats has nothing to do with alk), is another and huge question, where my opinion is that PO4 should never go below 0.02 as low PO4 is dangerous, but low NO3 is not dangerous, but rather bad if going to high in long term. So my ideal values are (my personal opinion):
KH:7-8 dKH
NO3:0-5 mg/l
PO4: 0.04-0.1 mg/l

Jonas

The reason I posted this thread is because there are articles outside of R2R on this very topic (nutrient levels to alkalinity levels) and I was curious about it.

Secondly, ask 10 people questions about the proper ALK parameter and you'll get 10 different answers.

 

[JonasRoman]

The reason I posted this thread is because there are articles outside of R2R on this very topic (nutrient levels to alkalinity levels) and I was curious about it.

Secondly, ask 10 people questions about the proper ALK parameter and you'll get 10 different answers.

Yes, but all 10 answers are not necessarily correct. Even if we can do things in several ways that doesnt mean its equal.

Concerning nutrient and alkalinity if someone say they are connected they need to explain themselves.

 

[Bear22]

Yes, but all 10 answers are not correct, haha. Even if we can do things in several ways that doesnt mean its equal.
Concerning nutrient and alkalinity if someone say they are connected I say no, and they need to explain themselves.

That's your take. You are familiar with the axiom about people's opinions right?

This topic has threads here in R2R, as well as the old school guy threads in Reef Community. Can't remember who it was (either Jason Fox or perhaps Chris Meckley) in a lengthy podcast talking about nutrient levels "bounced" against alkalinity levels and SPS health/growth rates.

Pretty certain that neither one of these guys "owe's" you an explanation. And I for one am going to listen to what they have to say since both do this for a living on a large scale versus me listening to some random dude on R2R.

 

[Bear22]

The only relationship that I am aware of is that if alk (and pH) are high, nutrients should not be too low or there is a risk of burnt tips on some SPS.

One hypothesis is that the skeleton grows faster than tissue can keep up if nutrients are too low.

This is the premise of my post, I was wondering if anybody has ever put any numbers to it in terms of ratios?

 

[Waldek M.]

Yes, but all 10 answers are not necessarily correct.

They are valid for each individual. One person may achieve success at one level, another at a different one. Every system is unique and depends on many factors. No one has yet determined the exact proportions and interdependencies involved.

 

[Bear22]

They are valid for each individual. One person may achieve success at one level, another at a different one. Every system is unique and depends on many factors. No one has yet determined the exact proportions and interdependencies involved.

Solid answer with no hubris detected ;-)

 

[EnterName]

Nutrient ratios (N:P) can only be measured roughly at home, even with the ULR/LR Hanna Checkers. At mid-range levels you get a ballpark figure (roughly ±20%), but at low levels the error becomes huge. This can even be proven mathematically.

I'm not sure this is getting any better when trying to relate nutrients to alkalinity. Let's say your tank has an alkalinity of 8dKH (142.8ppm CaCO₃). The "true ratio" columns show the ratio for the actual nitrate level. The "possible reading" column shows what the ratio could come out as, given the LR nitrate checker's accuracy of ±0.25ppm ±2% of reading:

True NO₃ (ppm)	True molar ratio CaCO₃ : NO₃	Possible reading (molar)	True mass ratio CaCO₃ : NO₃
1	88.5 : 1	69 - 120 : 1	142.8 : 1
2	44.2 : 1	38.5 - 51.6 : 1	71.4 : 1
3	29.5 : 1	26.7 - 32.8 : 1	47.6 : 1
4	22.1 : 1	20.4 - 24.1 : 1	35.7 : 1
5	17.7 : 1	16.5 - 19.0 : 1	28.6 : 1

The lower the nutrient level, the worse the relative error gets, because the fixed part of the error (±0.25ppm here) stays the same while the value shrinks. For phosphate it becomes even worse (ULR checker: ±0.02ppm ±5% of reading):

True PO₄ (ppm)	True molar ratio CaCO₃ : PO₄	Possible reading (molar)	True mass ratio CaCO₃ : PO₄
0.01	13550 : 1	4291 : 1 - ∞	14280 : 1
0.02	6775 : 1	3218 : 1 - ∞	7140 : 1
0.03	4517 : 1	2575 - 14228 : 1	4760 : 1
0.04	3388 : 1	2145 - 7114 : 1	3570 : 1
0.05	2710 : 1	1839 - 4743 : 1	2856 : 1
0.06	2258 : 1	1609 - 3557 : 1	2380 : 1
0.07	1936 : 1	1430 - 2846 : 1	2040 : 1
0.08	1694 : 1	1287 - 2371 : 1	1785 : 1
0.09	1506 : 1	1170 - 2033 : 1	1587 : 1

At 0.02ppm or below the checker can read 0.00, so the ratio has no upper limit at all
These ranges are worst cases from the manufacturer's specs only. They don't include the error of your alkalinity test. Also note the molar ratio counts CaCO₃ molecules; if you think in meq/L alkalinity, the numbers double.

I personally think ratios are very interesting, but we have to come to terms with the very limited accuracy of our tests.

 

[Bear22]

Nutrient ratios (N:P) can only be measured roughly at home, even with the ULR/LR Hanna Checkers. At mid-range levels you get a ballpark figure (roughly ±20%), but at low levels the error becomes huge. This can even be proven mathematically.

I'm not sure this is getting any better when trying to relate nutrients to alkalinity. Let's say your tank has an alkalinity of 8dKH (142.8ppm CaCO₃). The "true ratio" columns show the ratio for the actual nitrate level. The "possible reading" column shows what the ratio could come out as, given the LR nitrate checker's accuracy of ±0.25ppm ±2% of reading:

True NO₃ (ppm)	True molar ratio CaCO₃ : NO₃	Possible reading (molar)	True mass ratio CaCO₃ : NO₃
1	88.5 : 1	69 - 120 : 1	142.8 : 1
2	44.2 : 1	38.5 - 51.6 : 1	71.4 : 1
3	29.5 : 1	26.7 - 32.8 : 1	47.6 : 1
4	22.1 : 1	20.4 - 24.1 : 1	35.7 : 1
5	17.7 : 1	16.5 - 19.0 : 1	28.6 : 1

The lower the nutrient level, the worse the relative error gets, because the fixed part of the error (±0.25ppm here) stays the same while the value shrinks. For phosphate it becomes even worse (ULR checker: ±0.02ppm ±5% of reading):

True PO₄ (ppm)	True molar ratio CaCO₃ : PO₄	Possible reading (molar)	True mass ratio CaCO₃ : PO₄
0.01	13550 : 1	4291 : 1 - ∞	14280 : 1
0.02	6775 : 1	3218 : 1 - ∞	7140 : 1
0.03	4517 : 1	2575 - 14228 : 1	4760 : 1
0.04	3388 : 1	2145 - 7114 : 1	3570 : 1
0.05	2710 : 1	1839 - 4743 : 1	2856 : 1
0.06	2258 : 1	1609 - 3557 : 1	2380 : 1
0.07	1936 : 1	1430 - 2846 : 1	2040 : 1
0.08	1694 : 1	1287 - 2371 : 1	1785 : 1
0.09	1506 : 1	1170 - 2033 : 1	1587 : 1

At 0.02ppm or below the checker can read 0.00, so the ratio has no upper limit at all
These ranges are worst cases from the manufacturer's specs only. They don't include the error of your alkalinity test. Also note the molar ratio counts CaCO₃ molecules; if you think in meq/L alkalinity, the numbers double.

I personally think ratios are very interesting, but we have to come to terms with the very limited accuracy of our tests.

Interesting. I think it's safe to say much of our reef keeping is akin to being strapped to a chair, heads forward, and seeing lights and shadows across a cave wall (the allegory of the cave).

I guess what I am saying is that hobbyist testing is where the rubber meets the road in terms of outcome(s) and changes we make (test - make changes - test again - using the Mark 1 eyeball to observe changes).

Heck, even ICP test results between companies can have quite the variance.