Water Chemistry mystery: Unequal Dosing Calcium and Alkalinity

[Activeangel]

Hello,

First, I will say that nearly all my coral, including many SPS colonies have been growing strong for the past 1-2 years. Nonetheless, there is an interesting occurrence I would like to better understand. I seem to have to dose my Alk significantly more than Calc and still cant reach decent Alk levels.

My water parameters have been stable (testing with Red Sea Test Kits 2-5 times per week):
Amm/Nitrite/Nitrate = 0
Calc = 430-440 ppm
Alk = 7.3 dKH
Mag = 1480 ppm (see * below)

75 gallon mixed reef tank
I do ~7 gallon water changes about every 2 weeks with Red Sea Coral Pro Salt.
Dosing is done twice per day via a calibrated dosing pump:
Kent Liquid Calcium = 30 mL per day
Kent Pro Buffer dKH = 60 mL per day
*Kent Mag = stopped dosing 1 month ago as it always tested high... last week started coming down to just under 1400.

I'm switching off Kent and onto B-Ionic when my current gallons run out, and I'll provide feedback on any changes in the balance.
Nonetheless, does anyone have any advice as to how to get my Alk levels up to a normal level?

~Sharkey

 

[jrpark22000]

I dose twice as much (or more) ALK than I do CA. Quite a few people do similar. It's far from abnormal to do so.

 

[Irsug1]

Agreed. You probably don't want your alk higher than 8 anyway as you have 0 nitrates.

 

[madjoe]

If it aint broke dont fix it . I see nothing wrong with those numbers . U start changing stuff and bad things happen trust me tank crashing as we speak

 

[Activeangel]

Thanks everybody. That is very reassuring; I was under the impression most people dose approximately equal parts of each, and are able to reach 8.0 dKH (which is seemingly impossible for me to reach).

MadJoe -Sorry to hear that buddy! I wish you the best and hope you can mitigate the crash and salvage something.

 

[madjoe]

Thanks everybody. That is very reassuring; I was under the impression most people dose approximately equal parts of each, and are able to reach 8.0 dKH (which is seemingly impossible for me to reach).

MadJoe -Sorry to hear that buddy! I wish you the best and hope you can mitigate the crash and salvage something.

It can be reached but your at a safer level any way so id leave it . Stability is most important out of anything i was told dosing should be equal but in 10 yrs mine has never worked out to being equal. Thanks for the wishes hasn't completely crashed and im sure its human error so hopefully soon it will be back to normal fingers crossed lol crap happens i guess

 

[Paulip]

You have obviously factored in the increasing Alkalinity demands of your growing corals. The problem may be related to your pH levels. If I remember correctly, alkalinity is consumed in buffering your pH which was dependent on being in equilibrium with the cO2 in your home.

My brain is mush right , now. But,this might provide useful info.

http://www.advancedaquarist.com/2002/5/chemistry

 

[york3rdbase]

Have you checked your tests with a 2nd opinion? My alk home test was telling me my alk was at 7, even after massive water changes with reef crystals. Used my LFS as a 2nd opinion, their test kid read alk at 10.


Sent from my iPhone using Tapatalk

 

[Activeangel]

Great Point, Paulip! To be honest, I dont do any isolated tests for pH at the moment. I have Chaeto growing in my fuge and expect my tank is within parameters when my alk is.

However, I think the oxygen content inside my home is probably plenty high. I actually have 26 plants (including 4 trees) in the room with the tank, all hooked up on their own irrigation system, and growing strong. I would expect this decrease CO2, increase O2, and provide a rise in tank pH.

I think a high pH is usually associated with high carbonates, but my carbonates are low. If this is incorrect, please correct me.
--
Another good point York3rdBase,

Yes, I have verified my low alk with both my LFS's.

 

[Activeangel]

Quick thought!

My salinity is 1.024, and I know that higher salinity (literally) holds higher dissolved salts. It may only be a loose correlation, and not causation, but I will test raising my salinity to 1.025 for a period of time and see if my Alk rises with this increase. Also keeping in mind that even refractometers calibrated with RO water, such as mine, could be inaccurate at saltwater levels... so my 1.024 could even actually be slightly lower, and explain the lack of carbonate... I'm not sure if any of that was correct. It was just a thought.

 

[Paulip]

Your botanical garden sounds familiar. You wouldn't happen to have a 70 gallon that houses a leng sy monti on the far left and a highly flourescent birdsnest on the far right, would you?

 

[troublemaker]

Quick thought!

My salinity is 1.024, and I know that higher salinity (literally) holds higher dissolved salts. It may only be a loose correlation, and not causation, but I will test raising my salinity to 1.025 for a period of time and see if my Alk rises with this increase. Also keeping in mind that even refractometers calibrated with RO water, such as mine, could be inaccurate at saltwater levels... so my 1.024 could even actually be slightly lower, and explain the lack of carbonate... I'm not sure if any of that was correct. It was just a thought.

Don't calibrate with RO, calibration solution is cheap. This is kind of like diagnosing a gas car that is misfiring and never mentioning you filled it with diesel. You really need to start getting the basics in line before going after the rest.

 

[Paulip]

Quick thought!

My salinity is 1.024, and I know that higher salinity (literally) holds higher dissolved salts. It may only be a loose correlation, and not causation, but I will test raising my salinity to 1.025 for a period of time and see if my Alk rises with this increase. Also keeping in mind that even refractometers calibrated with RO water, such as mine, could be inaccurate at saltwater levels... so my 1.024 could even actually be slightly lower, and explain the lack of carbonate... I'm not sure if any of that was correct. It was just a thought.

By raising salinity, You will raise everything in similar proportions ( Calcium, Alkalinity, and Magnesium ) originally found in your salt. You get closer to the original salt mix's ratio/balance, but not as much as by simply doing a percentage water change.

I just put a quarter teaspoon of dry baking soda in the sump to get a 1 dkH boost and call it a day. Long term maintenance is made with the dose that comes from the ATO. Doing that manual 1 dkH per day may get you back in rythm to the true levels of Alk consumption in your tank.

Here is a calc to figure out how much dry baking soda you would need for a short term adjustment.
http://reef.diesyst.com/chemcalc/chemcalc.html

 

[Activeangel]

Thanks troublemaker, I didn't know calibration fluid was sold and had assumed most people simply calibrate with RO (after measuring and recording near-0 TDS of course). Because that is exactly what i'm looking for, I will take a look into some calibration fluid that is already calibrated near 1.025.

 

[Activeangel]

Oh, hey Paul; Yes, that's me. I just created this account not too long ago, and hope to start taking better photographs/videos as well as selling some of my nicer corals as they continue growing.

By raising salinity, You will raise everything in similar proportions ( Calcium, Alkalinity, and Magnesium ) originally found in your salt. You get closer to the original salt mix's ratio/balance, but not as much as by simply doing a percentage water change.
http://reef.diesyst.com/chemcalc/chemcalc.html

That's exactly what i expected. Because I have no problem controlling calcium and mag levels, I might try that to raise the Alk, and drop the calc/mag levels appropriately to a good balance... at least to start. I normally wouldn't want to add baking soda, but I will look into that link and consider it.