The Ways Alkalinity can Accumulate in a Reef Tank

Miami Reef

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"Why is my alkalinity rising?" is a seemingly simple question that consistently pops up in the chemistry section of Reef2Reef. However, it is a complex question since there are numerous ways alkalinity can accumulate - some ways one may least expect.

The consensus of an alkalinity range in home aquaria is from 7dKH to 12dKH. Going below this range may halt calcification (growth) in organisms containing calcium carbonate; stress corals with the lack of carbonate & bicarbonate in the water; may suppress pH, which can dissolve coral skeletons below about a pH of 7.5. In contrast, very elevated alkalinity can increase the likelihood of precipitation, thus, wasting the alkalinity solution and may stress certain organisms, especially ones without adequate nutrients in the water.

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Sodium bicarbonate: a common alkalinity additive.

First and foremost, the way alkalinity can climb in a tank is through deliberate dosing. If you add an alkalinity supplement, but the level rises above your comfort, the obvious solution is to reduce the dose. The amount of solution dosing exceeds the demand for the tank. Some salt mixes, like Instant Ocean's Reef Crystals or Red Sea's Coral Pro Salt, contain higher alkalinity. Water changes may unintentionally exacerbate the issue despite helpful intentions.

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An RO/DI system can help prevent unintentionally adding alkalinity to a tank.

Another way alkalinity is rising is due to your source water. Depending on where you live, your tap water can have a significant amount of alkalinity. For example, tap water containing 10dKH and a salt mix containing 10dKH can result in 20dKH saltwater. Continuously topping off your evaporation with tap water may gradually increase the resulting alkalinity.
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Elevating alkalinity due to low demand is a great excuse to stock up on corals.

The next way unanticipated elevated alkalinity occurs is from low-demand tanks. It is natural for organics in the sand to have a low localized pH, which dissolves the calcium carbonate. In a well-stocked tank, the amount of calcium and alkalinity added is negligible and unnoticed; however, if there isn't much demand, there can be an apparent rise over time. We expect long-term reefers to replenish their sand bed from the dissolution of calcium carbonate because of this process.

tempImagemnNyJn.png

My DIY carbon dosing solution: made with 1,000mL Vinegar, 250mL Vodka, and 4tsp Glucose


Subsequently, the processes of denitrification will increase alkalinity. Reefers who use denitrification systems such as:​
  • Dosing vodka, vinegar, or sugar.​
  • Implementing a sulfur denitrator.​
  • Merely containing a deep sand bed.​
For every 50ppm of nitrates depleted, you will add 2.3dKH of alkalinity. Note that nitrates consumed from the nitrification process/ammonia dosing/foods will result in an alkalinity net of zero. Ammonia converting to nitrates depletes the same amount of alkalinity that rises when the denitrification process adds it back. Dosing of nitrates skips the alkalinity-depletion step.

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Beginners can fall prey to marketing schemes.

Additionally, a frustrating way alkalinity unexpectedly accumulates is from deceitful products. Whether mislabeling products is because of a lack of understanding of chemistry from the manufacturers or from an immoral method of boosting sales, it only hurts us, the consumers. Here are only a few examples of mislabeled products:​
  • Aquavitro's OH balance. Claims to elevate pH by using a hydroxide blend solution without boosting alkalinity; it's incorrect because any hydroxide solution will dissociate and use CO2 to make carbonate and bicarbonate, resulting in alkalinity.​
  • Aquavitro's "calcification" is a calcium additive made from calcium gluconate. Despite not stating much about its effect on alkalinity, bacteria will metabolize gluconate, adding alkalinity.​
  • Brightwell's Boost pH+. "Works with buffers and alkalinity products to increase pH to desirable 8,3, 8.4 or 8.5 levels without increasing alkalinity itself." This statement on the bottle is false. Any additive that raises pH will also raise alkalinity.​
hi772-26-alkalinity-reagent.png

Throw out those expired test kits.

The final section will discuss how test errors and unique additives can impact alkalinity. The higher the salinity, the more abundant all the elements become. If you expect your salinity is around 35ppt, but in reality, it is higher due to a miscalibrated device, the alkalinity will be higher than expected (and so will all the other elements in the salt). Some alkalinity kits can test higher the older the regents become, so it is crucial to keep that in mind. The "unique" additives that may raise alkalinity are rocks made from cement, silica dosing (increases a trace amount), some amino acids, and other insignificant sources.

Although it can be frustrating to understand why your alkalinity is unintentionally rising, it can be satisfying once figured out. Elevated alkalinity can cause precipitation issues and can even have a snowball effect where fresh precipitation encourages more to form. Keeping alkalinity stable and in the optimal ranges make for happy and thriving organisms.

Happy Reefing! :)
 

Sean Clark

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Thanks, as someone that has used Aquavitro products for a long time (and still do), this gives me more insight as to the why of things. I never looked into to how the products worked and how they effected the rest of the system.
 

TheReefDiary

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My little 13.5g tank is currently using .5dkh per day. I have to dose 2ml daily to keep my alk high. Is it possible to build this up to a higher level over time and if so how long should I take to do it? Or should I just continue dosing what I am currently? Currently dosing 2ml nightly to keep alo at 8.3-8.4. when I test at night it's dropped to 7.8-7.9.

My pH in the tank is sitting between 8.3-8.5
 
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HankstankXXL750

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Very informative article. Thanks @Randy Holmes-Farley.

One question I have is on my 2 part dosing. If I neglect it for any amount of time, I will find a hard white extrusion from my dosing line. I assume this is a form of precipitate. Or is it just build up sort of like salt creep? Should that line terminate above the water level in my sump, or below water level.

Thanks.
 
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Miami Reef

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My little 13.5g tank is currently using .5dkh per day. I have to dose 2ml daily to keep my alk high. Is it possible to build this up to a higher level over time and if so how long should I take to do it? Or should I just continue dosing what I am currently? Currently dosing 2ml nightly to keep alo at 8.3-8.4. when I test at night it's dropped to 7.8-7.9.

My pH in the tank is sitting between 8.3-8.5
Those numbers are acceptable. If you want to increase your alkalinity, slightly raise your dose; your level will gradually increase over time.

Very informative article. Thanks @Randy Holmes-Farley.

One question I have is on my 2 part dosing. If I neglect it for any amount of time, I will find a hard white extrusion from my dosing line. I assume this is a form of precipitate. Or is it just build up sort of like salt creep? Should that line terminate above the water level in my sump, or below water level.

Thanks.
Usually, the alkalinity line gets precipitation. You should keep your dosing lines above the water for a few reasons: It will prevent crusting with localized calcium and eliminates the risk of a siphon. Periodically removing the crust shouldn’t be difficult. I’m glad you enjoyed my article. :)
 

HankstankXXL750

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@Miami Reef
First let me apologize for thanking Randy instead of you for the article lol. Probably because his name is in the forum title and it was late.

Yes it isn’t hard to clean the crusties but I seem to forget about those
Lines except when I clean my apex probes. I need to get it on the weekly schedule vs monthly or longer. I have automated so much, that cleaning the skimmer cup is about the only reason I have to get into the sump.

Been meaning to ask my question, but find other questions to ask or threads to follow so asked here as it was relevant.

Thanks for the article and the answer.
 
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Miami Reef

Miami Reef

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@Miami Reef
First let me apologize for thanking Randy instead of you for the article lol. Probably because his name is in the forum title and it was late.

Yes it isn’t hard to clean the crusties but I seem to forget about those
Lines except when I clean my apex probes. I need to get it on the weekly schedule vs monthly or longer. I have automated so much, that cleaning the skimmer cup is about the only reason I have to get into the sump.

Been meaning to ask my question, but find other questions to ask or threads to follow so asked here as it was relevant.

Thanks for the article and the answer.
No worries! I consider Randy as my mentor and I have no issues giving him credit as he inspired and taught me in many ways of reefing. :)


What are you dosing for alkalinity? I don’t have this problem and I haven‘t touch my lines in a few months. Could there be some splashing in the dosing line?
 

HankstankXXL750

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No worries! I consider Randy as my mentor and I have no issues giving him credit as he inspired and taught me in many ways of reefing. :)


What are you dosing for alkalinity? I don’t have this problem and I haven‘t touch my lines in a few months. Could there be some splashing in the dosing line?
I’m dosing seachem fusion1 and 2. Using apex dos with their reservoirs. Get a hard white buildup. Both tanks are Red Sea and both dose in a fairly calm area of the sump.
 
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Miami Reef

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I’m dosing seachem fusion1 and 2. Using apex dos with their reservoirs. Get a hard white buildup. Both tanks are Red Sea and both dose in a fairly calm area of the sump.
Are both fusion 1 and 2 causing the hard white build-up, or it is only one of the products?
 
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Miami Reef

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Just one. I believe it is the calcium
Perhaps consider switching to calcium carbonate and sodium carbonate for your 2 part needs. I believe the crusting will be negligible with that regime; it should be cheaper too.
 

HankstankXXL750

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Perhaps consider switching to calcium carbonate and sodium carbonate for your 2 part needs. I believe the crusting will be negligible with that regime; it should be cheaper too.
Started with this on recommendation of LFS that I buy most things from. Unfortunately they are 250 miles away so now I order most online. Gas prices ugh. So what brand etc do you use for alk, ca, mg?
 
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Miami Reef

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Started with this on recommendation of LFS that I buy most things from. Unfortunately they are 250 miles away so now I order most online. Gas prices ugh. So what brand etc do you use for alk, ca, mg?
I order most of my additives from Bulk Reef Supply. They use Randy’s original recipe for alkalinity and calcium; they use pharmaceutical-grade ingredients.

Here’s sodium carbonate: https://www.bulkreefsupply.com/1-gallon-mix-soda-ash-single-use-bulk-reef-supply.html

Here’s calcium chloride: https://www.bulkreefsupply.com/1-gallon-mix-calcium-chloride-single-use-bulk-reef-supply.html

Here are magnesium sulfate and chloride: https://www.bulkreefsupply.com/magnesium-mix-for-2-part-maintenance-bulk-reef-supply.html

If you have any other questions, feel free to make a new thread so we all can respond. :)

There are many different methods of dosing alkalinity and calcium; each have their own pros and cons: http://www.reefedition.com/the-many-methods-for-supplementing-calcium-and-alkalinity/
 

HankstankXXL750

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I order most of my additives from Bulk Reef Supply. They use Randy’s original recipe for alkalinity and calcium; they use pharmaceutical-grade ingredients.

Here’s sodium carbonate: https://www.bulkreefsupply.com/1-gallon-mix-soda-ash-single-use-bulk-reef-supply.html

Here’s calcium chloride: https://www.bulkreefsupply.com/1-gallon-mix-calcium-chloride-single-use-bulk-reef-supply.html

Here are magnesium sulfate and chloride: https://www.bulkreefsupply.com/magnesium-mix-for-2-part-maintenance-bulk-reef-supply.html

If you have any other questions, feel free to make a new thread so we all can respond. :)

There are many different methods of dosing alkalinity and calcium; each have their own pros and cons: http://www.reefedition.com/the-many-methods-for-supplementing-calcium-and-alkalinity/
I just started this thread if you would like to pitch in. Thanks.

 

Dburr1014

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I’m dosing seachem fusion1 and 2. Using apex dos with their reservoirs. Get a hard white buildup. Both tanks are Red Sea and both dose in a fairly calm area of the sump.
I get this also on the alkalinity side. I think it's just evaporation at the end of the line. Every few weeks I clean it off.
 

fk3212

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The water alkalinity within a saltwater aquarium is one of the most important chemical levels to keep track of. Not only does this measurement impact the water’s ability to neutralize acids, but it’s also a key component in maintaining a steady pH. The three ways you can reduce the alkalinity in you tank are:

1. Increase Your Water Changes
2. Test Alkalinity Frequently
3. Maintain Water Quality
 

Randy Holmes-Farley

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. The three ways you can reduce the alkalinity in you tank are:

1. Increase Your Water Changes
2. Test Alkalinity Frequently
3. Maintain Water Quality

Welcome to Reef2Reef!

FWIW, the first one only works, obviously, if the new salt water has lower alk than the tank. One can lower the alk in new salt water if there is a desire to lower alk using less salt water.

I'm not sure how #2 and #3 are solutions for those folks who experience increasing alk.
 

KrisReef

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"Elevating alkalinity due to low demand is a great excuse to stock up on corals."

Thanks @Miami Reef for provide much useful information and technical support for expanding my appreciation of coral husbandry. I think I can substitute your phrase quoted above to favorably convince the boss of the necessity of my binging. :)
 
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