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View Full Version : 2 Part Dosing, Alk is used but Cal stays same. Help


Vinno
10/13/2016, 09:47 AM
Hey guys,

Ive tested 3 times this month and after 1st and 2nd test, i added the alk mixture to the tank roughly to get alk of 8.0. My alk keeps dropping but my calcium kinda stays the same?

Ive quickly tested the salifer cal using plain tap water, turns color pretty quick.

what am i doing wrong here?

Tank stats:

4/10/16 (added alk after test)
---
Ph 8.15
Alk 7.6
Cal 450
Mag 1400

10/10/16 (added alk after test)
---
Alk 7.0
Cal 430

14/10/16 (none added, writing this post now)
---
Alk 7.0
Cal 430
Mag 1350

I will let the tank run another 4 days without doing nothing and see where its at again?

vhuang168
10/13/2016, 10:42 AM
Make sure you test at roughly he same time each time. Number at the start and end of day can be very different depending on tank setup.


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madweazl
10/13/2016, 10:52 AM
Make sure you test at roughly he same time each time. Number at the start and end of day can be very different depending on tank setup.


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Why would that affect measured Ca levels?

vhuang168
10/13/2016, 10:57 AM
Why would that affect measured Ca levels?



His CA levels are pretty steady but his Alk levels are varied. If it's uptake, both should vary.


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LJLKRL
10/13/2016, 11:11 AM
Mine did the same in my 55. Alk I had to dose, but not calcium. I had a good bit of coralline algae and read it uses alk. My corals and clam grew, but the calcium did not drop much. I just manually dosed every couple of weeks or as needed.

bertoni
10/13/2016, 01:52 PM
The drop in calcium is only 20 ppm per 2.8 dKH change in alkalinity. Unless the consumption rate is fairly high, water changes might be enough to keep the level up. The 1 dKH change in your numbers corresponds to about 7 ppm of calcium, which is within the error range of our test kits.

Vinno
10/13/2016, 09:19 PM
vhuang168, I will take test from same time, is it better when lights on or off?

Bertoni, about 2.4 alk dkh, so if I get what your saying 20ppm of calcium for every 2.8 alk, so I'm about right?

Won't be home for few days but will test again and let yous know. Thanks everyone.

bertoni
10/14/2016, 07:38 PM
Yes, that's about right.

Capt.Nemo
10/15/2016, 10:08 AM
I am having some similar issues. Dosing 2 part.....calcium has been fine and I can dose a reasonable amount for 2 days then day off, then again for couple days and day off. Calcium is maintaining 460. However, my Alk is refusing to come up, reading 2 different test kits. Was trying to bring up from 8 to 9.5 or so. 2 part states not to raise Alk by more than 1.4 dkh a day. I dose recommended amount to raise 1.4 and now I struggle to even get a reading. Color change is not as dramatic, but the best read I get is 6.0 ish. I am dosing every day. PH is hovering 8.0- 8.2, I can live with that, but Alk is killing me.

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bertoni
10/15/2016, 06:33 PM
You need to add more supplement. Lots of people dose more than 1.4 dKH per day. I dosed 2-3 dKH in one shot for years. I might break the dose into two parts, depending on what corals are in the tank.

Capt.Nemo
10/15/2016, 07:20 PM
Acripora, monty's, birds nests, frogspawn and few Poly's. I see you respond a lot here in the chemistry forum Bertoni, I have always got the impression, you know your stuff. So you say you dose 2-3 dkh in one shot, but break it into 2 parts??? So, if you needed a large dosage to hit your target, you break it up but still dose it through a 24 hour period? What would be your personal max dosage at 1 time? Sorry, just not understanding.

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bertoni
10/15/2016, 07:43 PM
I was dosing into a tank with soft corals, so 2-3 dKH was fine. I might try breaking the dose into three parts with those corals. Maybe one in the morning, before dinner, and one later in the evening. That's probably overkill, but hopefully, it's not that hard.

Vinno
10/29/2016, 10:37 AM
Ive added another 4-6 alk doses i think, been testing each one and calcium been the same. Tonight it finally went from 430 to 420.

My salifert about to run out so will buy another one in case of the calcium test is bad.

If its not bad test kit, what else am i doing wrong, say my corals arent growing but else uses up alk?

bertoni
10/29/2016, 04:45 PM
Coralline can consume a huge amount of alkalinity, and there might be some calcium carbonate buildup on walls, inside pumps, or on any heaters.

downbeach
10/30/2016, 04:08 AM
It's normal for you to see a decline in your alk more quickly than your Ca for a couple reasons. First is the fact that the uptake of Alk to Ca is a ratio of 5 parts alk (50ppm/2.8dKH) to every 2 parts Ca (20ppm), which is two and a half times more alk than Ca. Secondly, there is more Ca available in your system, for your system to draw on, so the decline in Ca appears to/and is less(~20ppm Ca to every 50ppm/2.8dKH alk). This includes, not only the uptake by your animals, but abiotic precipitation too. Testing variations to this is usually due to the accuracy of out hobby grade test kits, and individual differences in our testing procedures/process.
Another cause for these differences/imbalances is due to your WC's, and the accuracy of your SG, since the elements in your salt mix are going to be directly proportional to the SG you mix it to, i.e. make up water accurately mixed to a SG of 1.023 is going to have proportionally less Ca, Mg and Alk than if accurately mixed to a SG of 1.026. The amount of water changed and the frequency of those changes will also have their affect.
Due to these factor's I think you'd be better served to view your testing as a trend over time, considering all these factors, rather than a daily test and tweak method. Also, when dosing, the suggested daily limit to how much you can dose should include the normal amount your system uses each day, i.e. if your system uses 1.4dKH, and you're only adding 1.4dKH, then all you're doing is keeping up with the demand. So, you would need to add the suggested daily limit(1.4dKH in the case of alk)to your normal daily uptake to see an increase.

Here is a good article worth a read:

http://reefkeeping.com/issues/2004-12/rhf/index.php