Calcium dropping faster than alkalinity

jk_s124

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Ever since I have started dosing two part, I have experienced a faster decline in calcium than alkalinity. I’ve searched the forums and the internet, but it seems as this is not a normal issue. Have a 29 gallon coralife biocube that has been running for two and a half years. Mixed reef with a fair amount of sps. I initially relied on kalk mixed with my ato water but eventually needed to add two part. I have a canopy which limits the amount of evaporation. About three gallons every two weeks.

I dosed two part with fully saturated kalk ato water until three weeks ago. It was always a challenge to dial in my two part. My calcium especially. A few months ago I moved my dosing lines to a more high flow area, but I still had the calcium issue. Next I stopped with the kalk in my ato. This seemed to level things off for about three weeks. This week though my calcium dropped from 400 (which it had been holding steady for 3 weeks) to 380. Tested several times. My alkalinity has held between 7.8 and 8.4. Mag was tested at 1320.

I don’t dose for magnesium because my magnesium levels have always appeared to reamain consistent. I do 5 gallon weekIy water changes and assumed this would be enough to supplement the magnesium. I havent noticed any recent signs of precipitation. So any ideas in what may be causing the calcium levels to be dropping? Thanks!
 

homer1475

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Checked your sandbed for clumping?

Had the same issue long time ago when I was a n00b, ended up turning my sandbed to rock. It's more then likely precipitating out.

This was my sandbed when I removed it, and yes thats sand, not rock.
20171205_113912.jpg
 
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jk_s124

jk_s124

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I vacuum my sand bed every water change. I have not noticed any clumping. That being said, I assume it must be precipitation as well, I just can’t seem to pinpoint what is causing it or how to fix it.
 
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jk_s124

jk_s124

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Look on your heaters, and inside pumps/powerheads for white(almost yellow) crust.
I’ve never had a problem with precipitation on equipment. I do regularly break down my powerheads and clean in citric acid. Would be a good reason though to do it again tonight. I’ll check my heater as well. I know I have some spirobid worms that should be scrapped off right now.
 

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+-10ppm Ca is about the level to which I'd trust a titration test kit.
So I'd need to see more than 400->380 to convince myself there was an actual imbalance.
 
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jk_s124

jk_s124

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+-10ppm Ca is about the level to which I'd trust a titration test kit.
So I'd need to see more than 400->380 to convince myself there was an actual imbalance.

That is possible. I’m alerted to it more likely than not because this seems to be a chronic issue. Hopefully everything is fine and Im just being paranoid.
 
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jk_s124

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In the past when this has occurred I would hand dose 30 mls or so calcium to bump my level back up. Usually after two weeks or so I would be low again. I’ve only been running without kalk for three weeks so maybe I need to give it more time to see if my calcium level really is depleting faster.
 

Randy Holmes-Farley

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There is no possible mechanism, no type of precipitation or anything else, for calcium to decline faster than alkalinity at a rate of 18-20 ppm calcium for each 2.8 dKH of alkalinity.

The possible explanations are:

1. Mismade solutions or dosing pump delivery mechanisms.
2. You are adding alkalinity somehow (such as nitrate dosing or nitrate decline, tap water, additives, etc.)
3. Water changes are messing with the ratio.
4. Test error.
 

Randy Holmes-Farley

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Ever since I have started dosing two part, I have experienced a faster decline in calcium than alkalinity. I’ve searched the forums and the internet, but it seems as this is not a normal issue. Have a 29 gallon coralife biocube that has been running for two and a half years. Mixed reef with a fair amount of sps. I initially relied on kalk mixed with my ato water but eventually needed to add two part. I have a canopy which limits the amount of evaporation. About three gallons every two weeks.

I dosed two part with fully saturated kalk ato water until three weeks ago. It was always a challenge to dial in my two part. My calcium especially. A few months ago I moved my dosing lines to a more high flow area, but I still had the calcium issue. Next I stopped with the kalk in my ato. This seemed to level things off for about three weeks. This week though my calcium dropped from 400 (which it had been holding steady for 3 weeks) to 380. Tested several times. My alkalinity has held between 7.8 and 8.4. Mag was tested at 1320.

I don’t dose for magnesium because my magnesium levels have always appeared to reamain consistent. I do 5 gallon weekIy water changes and assumed this would be enough to supplement the magnesium. I havent noticed any recent signs of precipitation. So any ideas in what may be causing the calcium levels to be dropping? Thanks!

What two part are you dosing?

Not all are designed for 1:1 dosing.
 
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jk_s124

jk_s124

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What two part are you dosing?

Not all are designed for 1:1 dosing.
Bulk reef supply. I don’t dose any other additives. I have experienced this through several Red Sea test kits. So I suppose mechanical then. I’ll will have to test my dosing pumps and make sure they are dosing at the same rate. Any other mechanical possibility? I have observed the dosing of both calcium and alkalinity so I’m sure the lines are connected. I guess I could be doing something wrong with how I mix the solution as well. I’ll have to review that too. Thanks randy.
 

Randy Holmes-Farley

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Bulk reef supply. I don’t dose any other additives. I have experienced this through several Red Sea test kits. So I suppose mechanical then. I’ll will have to test my dosing pumps and make sure they are dosing at the same rate. Any other mechanical possibility? I have observed the dosing of both calcium and alkalinity so I’m sure the lines are connected. I guess I could be doing something wrong with how I mix the solution as well. I’ll have to review that too. Thanks randy.

If the solutions were not made at the exact right volumes, dosing won't be equal.

Are you dosing anything else?

Water changes?
 
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jk_s124

jk_s124

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Not dosing anything else. Rodi water that reads 0 tds. Mix the one gallon pouches in one gallon containers. I do 5 gallon weekly water changes. I use regular instant ocean salt mix. Specific gravity is 1.026.
 

Randy Holmes-Farley

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I use regular instant ocean salt mix. Specific gravity is 1.026.

Bingo. That's a likely cause.

Regular Instant Ocean is a fine mix and I used it for 20 years, but it is a high alk, low calcium mix. hence it would skew the apparent demand toward more calcium than alkalinity.

Part of the reason I used it is because I wanted a low calcium high alk mix to offset the fact that I used limewater (kalkwasser) for all calcium and alkalinity, and over time that skews toward a little too much calcium dosed relative to alkalinity. Thus, the water changes offset the salt mix issues.
 
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