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Old 09/19/2018, 02:06 PM   #1
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DKH help

Hi everyone,

I am considering setting up a automatic dosing system in preparation for buying more corals, I have a 120g tank, running for 10months now. Contains around 10 fish, 5 soft corals and 6 LPS corals.

I've measured my calc, mag & alk for the last 3 days at the same time and it's come out as follows.

Calc - 420 / 420 / 420
Mag - 1260 / 1260 / 1260
DKH - 7 / 6.85 / 6.7

I know my alk is too low but as it's dropping steadily should I start dosing just alk and leave the others to water changes?

I change 15% water every two weeks with red sea salt.

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Old 09/19/2018, 03:23 PM   #2
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Perfectly fine to just dose ALK.

80G SCA Build:

Originally posted by der_wille_zur_macht:

"He's just taking his lunch to work"
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Old 09/19/2018, 06:01 PM   #3
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I agree. Dosing just the alkalinity should be okay. I'd watch the calcium level from time to time, and the SG, since the alkalinity supplement will raise it.

Jonathan Bertoni
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Old 09/20/2018, 02:47 PM   #4
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Calcium drops much slower than dKH and anything from about 380 to 440 is fine.


180 gallon, 30 gallon sump, 3 250W MH + 4 ATI T5's, MTC MVX 36 Skimmer, Apex controller Reef Octopus CaRx

Current Tank Info: 2 Barred Rabbitfish, Yellow/Purple, McMaster Fairy, Carpenter, Red Head,Red Fin, Hoevans, Possum, 2 Leopard Wrasses, Kole, Purple & Atlantic Blue Tangs, Matted Filefish, 2 Percula Clown, 4 PJ and2 Banggai Cardinalfish , Swallowtail and Bellus Angel,
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Old 09/21/2018, 10:46 AM   #5
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I agree with all above. Every time you purchase sps or lps you should test all 3 elements often. Once you get the consumption, you can move to once a week, then once a month. Auto-dosing will fail you if you don’t test promptly.

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Old 09/22/2018, 01:01 PM   #6
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3 days testing is not long enough to validate consumption.
I tested weekly for 3 months to understand consumption
Red Sea mixes high in the range, your ALK should be maintained in conjunction with you nitrate levels, usually higher nitrates like 5-10 ppm Alk better lower in the range but not exceeding 8.5 so your not far off. I would want to rule out testing errors first and this just takes time

Measure your levels both before and after water change, and record.

Most important is the stability, especially the ALK

I see only 6 corals (now) that would use ALK/CA so not a big load.

For example, I have 10 SPS, three clams, and 40LPS in a 70g and my daily consumption is only 5 ppm for both

I can’t count the number of corals people killed with excessive dosing regimes that existed because consumption rates were inaccurate. Take your time, manually dose, add some corals, test, record, see what the longer term pattern is, then automate if that makes sense

Last edited by Uncle99; 09/22/2018 at 01:21 PM.
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Old 09/22/2018, 03:31 PM   #7
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I agree that 3 days is only a few data points, but 3 months is long enough that animal growth might change the consumption rate quite a bit, especially in a newer tank. I'd measure every day for a few days, then slowly back off to once a week or once a month, depending on the tank in question, and how often new inhabitants are added.

I agree that adding new animals is a good time to test more frequently for a bit, especially if they are stony corals or the like.

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