Better understanding of Alkalinity- Help needed

[Reefahholic]

Quick Definition:

Alkalinity is a chemical measurement of a water's ability to neutralize acids. Alkalinity is also a measure of a water's buffering capacity or its ability to resist changes in pH upon the addition of acids or bases.

So I watched this video (link below) a while back and it bothered me since that day. Jake tested his water and his ALK level was extremely low. Like abnormally low for a reef tank. However, the corals were all doing amazing.



When I have a low ALK level, I simply dose ALK to bring it up. If it's a huge jump (which never happens because I test weekly and dose my system daily) I begin to bring it up slowly.

I use Instant Ocean salt-mix. The ALK level of that salt if mixed to 1.026 tests around 10.0 dKH. I like to run my tank at 8-9 dKH. So I use Muriatic acid to lower the ALK to my desired level. 5ml will lower approx 40 gallons of water by about 1 dKH. Why? Because I'm cheap. :p I'd love to have a salt that mixes to my desired ranges, but salt-mix gets expensive. Good ol' IO is about the cheapest good quality salt out there. :D

So anyway, I don't have any issues raising or lowering my ALK level. At least I haven't yet. Can somebody help me to better understand what was happening in Jakes tank. Why was his ALK that low and why couldn't he simply bring that level up to say 8 dKH? Any help would be appreciated as I really don't have a deep understanding of ALK / PH balance. ;Bookworm

 

[NS Mike D]

he is dosing everyday which means the corals are using up bicarbonates everyday. I'll take a pass on the chemistry but I do know that alk tests are actually a surrogate test and they there are other minor factors that go into reef chemistry (ie other forms and Ca and C that corals can use to make form skeletons).

I think the big takeaway here is that his tank is stable to the level that his tests come up with the same number and that he relioes more on what his corals are telling him that making adjustments merely due to test results.

PS I have read many articles about targeting ALK to coincide with NO3 & PO4 - that is if you nutrients are high, target a higher alk , in a low to no nutrients tank (common with sps tanks) target low alk. This is debatable, but I see this correlation too often to ignore.

 

[Reefahholic]

Thx NS Mike. That makes sense.

 

[Reefahholic]

he is dosing everyday which means the corals are using up bicarbonates everyday. I'll take a pass on the chemistry but I do know that alk tests are actually a surrogate test and they there are other minor factors that go into reef chemistry (ie other forms and Ca and C that corals can use to make form skeletons).

I think the big takeaway here is that his tank is stable to the level that his tests come up with the same number and that he relioes more on what his corals are telling him that making adjustments merely due to test results.

PS I have read many articles about targeting ALK to coincide with NO3 & PO4 - that is if you nutrients are high, target a higher alk , in a low to no nutrients tank (common with sps tanks) target low alk. This is debatable, but I see this correlation too often to ignore.

He acted like he couldn't > the ALK level. Would it not be easy to add ALK and bring that level up as high as you wanted it?

 

[NS Mike D]

He acted like he couldn't > the ALK level. Would it not be easy to add ALK and bring that level up as high as you wanted it?

Couldn't say for sure, but I get the idea with go what with your tank is telling you and don't muck things up - since he's already dosing a buffer, and the corals are doing well, he OK with alk at 6. He implied he has tried to raise it, but decided since whatever he did, didn't work and decided his tank was better off with where it was, alk wise.

remember, adding part a to raise alk can result in a precipitation and both alk and Ca dropping. Sometimes merely adding alk can backfire.

Calcium and carbonates naturally want to get together (corals break down the bicarbonates into carbonates and combine with calcium to form skeletons). Mg keeps the bicarbonates and CA suspended as ions in the water. There is a point where Mg cannot do that and a precipitation of alk and CA combine and drop out of the water column.

I'll let the chemist chime in, but I suspect there is more that just simple ratios that keep the ions suspended.

 

[Reefahholic]

He implied he has tried to raise it, but decided since whatever he did, didn't work and decided his tank was better off with where it was, alk wise.

This is the part I don't understand. Is it possible that you can't raise Alk? Why?

I've never had this happen have any of you guys?

 

[Reefahholic]

I just reached out to Jake about it on that YouTube video. We'll see what he says.

I've never seen a TOTM where a reefer reported his ALK level to be 4.8 and says he just leaves it there because he can't raise it.

This is just odd. I hope Randy will explain this to where I can understand. Maybe Jake can respond too. Jake is no rookie so there's got to be a logical reason behind it as to why he would leave it that low and not at least increase it to 7 or 8 "even if" the corals are doing good.

 

[NS Mike D]

I just watched again to see if he leaves any clues to what's up with his alk. I saw that it was not 6dkh as he predicted but 4.8. Yesterday I was reading an article on ALK and how coral will grow in a wide range of alk, it does stop at and below 7. He was guessing 6 on he basis that the acro tips and monties were showing signs of growth, in line with his past observations of 6.

meanwhile CA (520) and Mg (1410) so it's not a precipitation.

His dosing technique is "eyeball" and not measured with any degree of accurate measurements against consumption. Alk will be consumed faster that CA.

IMO, he's underestimating the increase in ALk consumption when he increases his buffer dosing. Since he's at or below limiting levels of growth and we know his corals are consuming what he's dosing, it's possible that additional ALK will be consumed by an increase in growth activity of the corals and thus not show as increase in test results until his increase dosing exceeds the increase in consumption.

So other other explanations, but less likely:

@Randy Holmes-Farley posted this in another thread:

"Otherwise, there are a few ways alkalinity can decline and not see a calcium drop, such as increasing nitrate (not just high, but actually rising) or the use of a sulfur denitrator."

 

[Reefahholic]

I just watched again to see if he leaves any clues to what's up with his alk. I saw that it was not 6dkh as he predicted but 4.8. Yesterday I was reading an article on ALK and how coral will grow in a wide range of alk, it does stop at and below 7. He was guessing 6 on he basis that the acro tips and monties were showing signs of growth, in line with his past observations of 6.

meanwhile CA (520) and Mg (1410) so it's not a precipitation.

His dosing technique is "eyeball" and not measured with any degree of accurate measurements against consumption. Alk will be consumed faster that CA.

IMO, he's underestimating the increase in ALk consumption when he increases his buffer dosing. Since he's at or below limiting levels of growth and we know his corals are consuming what he's dosing, it's possible that additional ALK will be consumed by an increase in growth activity of the corals and thus not show as increase in test results until his increase dosing exceeds the increase in consumption.

So other other explanations, but less likely:

@Randy Holmes-Farley posted this in another thread:

"Otherwise, there are a few ways alkalinity can decline and not see a calcium drop, such as increasing nitrate (not just high, but actually rising) or the use of a sulfur denitrator."

It's possible that additional ALK will be consumed by an increase in growth activity of the corals and thus not show as increase in test results until his increase dosing exceeds the increase in consumption.

This is exactly what I was thinking. Why not figure out the demand and increase it to the appropriate dosage.?

 

[NS Mike D]

This is exactly what I was thinking. Why not figure out the demand and increase it to the appropriate dosage.?

I thought the same thing, then looked at his tank and then mine and withdrew the question.

And let's examine the question. What is the appropriate level?

If 6 dkh is resulting in a tank like that, why raise it other than conventional wisdom says corals can't grow below 7dkh.

7 dkh is a stagnant number. It's not 7dlk (or any fixed target number) that is important, but rather consumption of alk. i e providing sufficient ALK for the corals to grow, So regardless of the target number (and since we know its a low alk sps tank let's assume is a ultra low nutrient tank as well) the only thing that matters is to maintain that number to match consumption.

So in Jakes case, if his corals are growing and doing very well dosing at a rate that maintains 6dkh, doesn't that become the appropriate dosage for his tank?

In practice that makes total sense to me, but I would screw that up and continue to increase my alk dose until I broke 7dkh and probable kill the corals in the process and friends come over I can show off my algae experiment.

 

[Reefahholic]

I thought the same thing, then looked at his tank and then mine and withdrew the question.

And let's examine the question. What is the appropriate level?

If 6 dkh is resulting in a tank like that, why raise it other than conventional wisdom says corals can't grow below 7dkh.

7 dkh is a stagnant number. It's not 7dlk (or any fixed target number) that is important, but rather consumption of alk. i e providing sufficient ALK for the corals to grow, So regardless of the target number (and since we know its a low alk sps tank let's assume is a ultra low nutrient tank as well) the only thing that matters is to maintain that number to match consumption.

So in Jakes case, if his corals are growing and doing very well dosing at a rate that maintains 6dkh, doesn't that become the appropriate dosage for his tank?

In practice that makes total sense to me, but I would screw that up and continue to increase my alk dose until I broke 7dkh and probable kill the corals in the process and friends come over I can show off my algae experiment.

I agree with most of what you said. I just feel like slowly raising the dKH from 4.8 to 7 or 8 will not kill the coral and will be more benificial for the coral in the long run. If we are not concerned with ultra low Alk levels and there’s no range that corals should grow and thrive in and we’re basing everything off of visuality, what’s the point of testing? IMO, we all test because we know there’s a specific range where corals thrive and do the best at. Of course, with everything there are exceptions and we know corals can and will adapt. Why make them adapt? Why not provide the best parameters we can and “not” let them dip to abnormally low levels?

I guess for me it really doesn’t make sense. Here’s a few analogies. I can push my car past the normal oil change, tire changes, belt changes, etc. The car may do OK for a while, but eventually I’ll be stranded, because instead of allowing myself some wiggle room, I drove the limits to the very edge until finally the disaster happened. I’ll I’m saying is that I like to build my house on the rock and not sand. :p

Jake...please raise your Alk level sir. That tank looks too good to have a crash. :D

 

[Reefahholic]

Jake’s reply :D

 

[John Hanna]

remember, adding part a to raise alk can result in a precipitation and both alk and Ca dropping. Sometimes merely adding alk can backfire.

You'll end up with precipitation when a saturation level is present or concentrations of both Alk (CO3) and Calcium are high forming the insoluble CaCO3. Since his tank is low in Alk, this precipitation will not occur in excess to warrant not adding any additional alk supplement.

IMO, he's underestimating the increase in ALk consumption when he increases his buffer dosing. Since he's at or below limiting levels of growth and we know his corals are consuming what he's dosing, it's possible that additional ALK will be consumed by an increase in growth activity of the corals and thus not show as increase in test results until his increase dosing exceeds the increase in consumption.

So other other explanations, but less likely:

@Randy Holmes-Farley posted this in another thread:

"Otherwise, there are a few ways alkalinity can decline and not see a calcium drop, such as increasing nitrate (not just high, but actually rising) or the use of a sulfur denitrator."

With regard to the quote from Randy, I believe this was due to an increase in bacteria growth or other organisms which use carbon sources but not calcium therefore declining alk but not Ca. This would also produce CO2 pushing the pH down.

From what I gathered in his Video, his primary source of calcium is Kalk (~3min mark), which contributes to a high pH. He then supplements with an alk buffer either Bicarb or Carbonate to increase his alk. He did say that he increased the concentration of his alk buffer so he can definitely change were it sits at long term. There is no reason in my opinion why he can't bring it to normal ranges.

http://reefkeeping.com/issues/2005-03/rhf/index.php - Check out Fig. 3 and 4.

1. If he adds too much carbonate, he will continue to boost his pH up, which will then lead to greater precipation and too high of a level long term. Since both his calcium and pH is on the high end, my recommendation would be to drop the kalk level and increase carbonate + CaCl to compensate the drop in both pH and Ca levels.

2. If you check out Fig. 5 in the link below, he would be sitting in Zone 4 - therefore he should try supplementing Bicarb
https://www.advancedaquarist.com/2002/11/chemistry

In both scenarios, there is no reason I can see why he wouldn't and/or can't add any additional alk buffers. In tanks with high growth demand, the main long term issue would be salinity increases from sodium accumulation used in the buffers. Think of it like eating an orange, you eat the inside flesh but leave the skin... eventually the level of skins will accumulate, while the flesh is absorbed for growth. Since his pH is in the correct zone, the ratio of carbonate to bicarbonate remain within usable ranges for the corals, though the quantity of ions available for uptake by coral is very low. See Fig 7. to explain this concept.

http://reefkeeping.com/issues/2006-06/rhf/index.php

Cheers,
John

 

[Reefahholic]

:)Wow, thx for that John. :-) Your knowledge is far above mine in this area. Appreciate you taking the time to respond.

You'll end up with precipitation when a saturation level is present or concentrations of both Alk (CO3) and Calcium are high forming the insoluble CaCO3. Since his tank is low in Alk, this precipitation will not occur in excess to warrant not adding any additional alk supplement.



With regard to the quote from Randy, I believe this was due to an increase in bacteria growth or other organisms which use carbon sources but not calcium therefore declining alk but not Ca. This would also produce CO2 pushing the pH down.

From what I gathered in his Video, his primary source of calcium is Kalk (~3min mark), which contributes to a high pH. He then supplements with an alk buffer either Bicarb or Carbonate to increase his alk. He did say that he increased the concentration of his alk buffer so he can definitely change were it sits at long term. There is no reason in my opinion why he can't bring it to normal ranges.

http://reefkeeping.com/issues/2005-03/rhf/index.php - Check out Fig. 3 and 4.

1. If he adds too much carbonate, he will continue to boost his pH up, which will then lead to greater precipation and too high of a level long term. Since both his calcium and pH is on the high end, my recommendation would be to drop the kalk level and increase carbonate + CaCl to compensate the drop in both pH and Ca levels.

2. If you check out Fig. 5 in the link below, he would be sitting in Zone 4 - therefore he should try supplementing Bicarb
https://www.advancedaquarist.com/2002/11/chemistry

In both scenarios, there is no reason I can see why he wouldn't and/or can't add any additional alk buffers. In tanks with high growth demand, the main long term issue would be salinity increases from sodium accumulation used in the buffers. Think of it like eating an orange, you eat the inside flesh but leave the skin... eventually the level of skins will accumulate, while the flesh is absorbed for growth. Since his pH is in the correct zone, the ratio of carbonate to bicarbonate remain within usable ranges for the corals, though the quantity of ions available for uptake by coral is very low. See Fig 7. to explain this concept.

http://reefkeeping.com/issues/2006-06/rhf/index.php

Cheers,
John