Low Alkalinity Yet Normal range of calcium?

[FellowSclownfish20270]

Hello everyone,

I have done a 25% water change in my 40 gallon breeder reef tank yesterday night and waited for tomorrow to test my parameters.

During this time, I have tested my Calcium, Alkalinity and Magnesium.

My results from testing came out as:
Calcium: 450
Alkalinity: 7.0
Magnesium: 1350
I have tested my Alkalinity 3 times today because I was surprised that my Alkalinity was low.
My Alkalinity testing from last week was 8.9. Yet I never expected it to go down to atleast a 7.0.
Do I need to dose Alkalinity to rise its result? If so, which brand would you guys recommend because I’m a new to dosing. If anyone knows why Alkalinity drops, I would love to know.
Thanks.

 

[Miami Reef]

The recommended range for alkalinity is 7-11dLH, so your result is fine for now. You can raise the level if you’d like.

Coralline algae and stony corals use alkalinity (as bicarbonate) to make their skeletons.

Do you have corals in your tank?

 

[Twoddler]

What's the alk of the salt you use ?

 

[FellowSclownfish20270]

The recommended range for alkalinity is 7-11dLH, so your result is fine for now. You can raise the level if you’d like.

Coralline algae and stony corals use alkalinity (as bicarbonate) to make their skeletons.

Do you have corals in your tank?

I don’t have any corals but I do have a Rose Bubble Tip Anemone in my tank

 

[dschuffert]

Something I learned from the Fauna Marin Knowledgebase has served me well over many years. The salinity value also matters when examining the relationship between alkalinity and calcium. Copied the following from their site (https://www.faunamarin.de/en/knowledge-base/):

Measured value relation to 35 psu​

All water values given as reference values in tests or in literature are based on the assumption of a certain salt concentration. The average value of 35 psu which is usually found in natural seawater serves as a basis. This means that 35 grams of salts are dissolved in 1 liter (0,26 US.liq.gal.) of water. Learn more under “Salinity”.

The lower the salinity of the water, the lower the concentration of all macro elements dissolved in it. For trace elements, the salt content is of less importance because their concentration will still be sufficient for physiological processes even with lower salt density. However, the important elements such as calcium, magnesium, strontium etc. are proportionally reduced by low salt content.

An example:

Salt concentration (salinity) 30 psu – Calcium concentration 380 mg/l(0,26 US.liq.gal.) – Relational value 12.6

Salt concentration (salinity) 35 psu – Calcium concentration 440 mg/l(0,26 US.liq.gal.) – Relational value 12.6

Despite different calcium values, both relations are the same, and therefore also the low value of 30 psu is ok. The relational values at 35 psu are therefore very important to show if the measured value is tolerable according to the value relation. Otherwise it will be necessary to perform a supplementation accordingly.

The most important macro elements are summarized in a table called salinity line. This makes it quick and easy to see which water value needs to be adjusted and which ones are in the ideal range.

 

[Miami Reef]

Purchase Baking Soda from the grocery store.

You can use this calculator to determine how much you want to raise the alk: https://www.bulkreefsupply.com/reef-calculator/alkalinity-calculator-reef

Select dry sodium bicarbonate. You can dissolve it in water prior to adding it.

 

[FellowSclownfish20270]

What's the alk of the salt you use ?

The Salt I use is Instant Ocean Reef Crystals though the bag doesn’t say anything about the alkalinity. Though I mix it in a bucket for about at least overnight and test the salinity which it usually stays exactly at the same temp as my tank. I dont exceed the amount of salt I put in, I only add about 5 gallons of salt into the bucket!

 

[Twoddler]

Your bta will not like swings in alk, to make things simple I would measure the alk in a fresh mix of saltwater, (mixed correctly).
That measurement DKH is your target alk ( if you need to do a large water change you won't have a large swing in alk )
If for example your new salt measures 8 DKH and you find it's dropping then consider dosing or frequent 10% water changes.
Stability is key

 

[dr_vinnie_boombatz]

What are you using to test ALK? If Hanna maybe your reagent went bad?

 

[dr_vinnie_boombatz]

The Salt I use is Instant Ocean Reef Crystals though the bag doesn’t say anything about the alkalinity. Though I mix it in a bucket for about at least overnight and test the salinity which it usually stays exactly at the same temp as my tank. I dont exceed the amount of salt I put in, I only add about 5 gallons of salt into the bucket!

Instant Ocean salt stinks in my opinion, I recently switched from their regular because it had super high mg. ALK was too high too, I like running 8

IO doesn't even list their parameters, looking online reef crystals has ALK of 13!?

 

[FellowSclownfish20270]

What are you using to test ALK? If Hanna maybe your reagent went bad?

I test my parameters with Saliferts testing kits.

 

[FellowSclownfish20270]

Your bta will not like swings in alk, to make things simple I would measure the alk in a fresh mix of saltwater, (mixed correctly).
That measurement DKH is your target alk ( if you need to do a large water change you won't have a large swing in alk )
If for example your new salt measures 8 DKH and you find it's dropping then consider dosing or frequent 10% water changes.
Stability is key

That sounds straight on point! Thanks!

 

[gbroadbridge]

Do I need to dose Alkalinity to rise its result? If so, which brand would you guys recommend because I’m a new to dosing. If anyone knows why Alkalinity drops, I would love to know.
Thanks.

The simplest and cheapest way to raise Alkalinity is food grade baking soda from the grocery store.

The is no need to buy something expensive from an LFS.

There is a link to a calculator posted above.

 

[Randy Holmes-Farley]

I really don’t see anything unusual or problematic or any reason the blame the salt mix as being bad.

If you start at 450 ppm calcium and 10 dKH, and some calcium carbonate is produced, you get to 430 ppm calcium and 7 dKH.

Keep in mind that all of our test results can have substantial error associated with them.

Calcium is good at 400-550 ppm and alk at 7-11 dKH (IMO), so if you are anywhere in those ranges things are fine.

 

[dr_vinnie_boombatz]

I test my parameters with Saliferts testing kits.

Have you ruled out your test kit is wrong or went bad?

 

[dr_vinnie_boombatz]

OP had 8.9 ALK one week ago, its say it went down -25% over the week. That would be 6.67 ALK. Did a 25% WC so -1.66 ALK got removed with the old saltwater = 5.01 ALK, add in new saltwater that has 13 ALK, that is +3.25 ALK, so should be ~8.26 ALK, no?

7 ALK on the test assumes ~40% of ALK got used in a week. Is this realistic?

 

[Randy Holmes-Farley]

7 ALK on the test assumes ~40% of ALK got used in a week. Is this realistic?

Alk can decline 1-3 dKH per day, or more, depending on what is in the tank, so yes.

 

[dr_vinnie_boombatz]

Alk can decline 1-3 dKH per day, or more, depending on what is in the tank, so yes.

OP said there are no coral, only one anemone. Could that consume that much in a 40g? Unless the tank is full of coralline too

 

[Randy Holmes-Farley]

OP said there are no coral, only one anemone. Could that consume that much in a 40g? Unless the tank is full of coralline too

Precipitation of calcium carbonate can do more than what I posted, and is especially common in new tanks. Rising nitrate also depletes alk.

That said, I don’t know why his alk declined, and the amount doesn’t seem unusual to me. If he wants alk above 7 dKH, then dosing is the answer since water changes are an expensive way to boost alk.

 

[FellowSclownfish20270]

The simplest and cheapest way to raise Alkalinity is food grade baking soda from the grocery store.

The is no need to buy something expensive from an LFS.

There is a link to a calculator posted above.

Hi! I did this a week ago, I used carbonated baking soda ash that i used from my local grocery store! I dosed about 1 ml the first day and waited until tomorrow, tested same result. Dosed 1 ML again and tested, same result. So far what i did was mix some freshly salt water and poured in 3 cups of salt water into the tank. I waited 4 days and tested again. My Alkalinity levels are now at 8.6!