Why is my alkalinity suddenly dropping?

Joe Batt

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My alkalinity as suddenly started to drop like a stone, but no sign of precipitation, and dosage goes into good flow area. I don't know why.

I maintain my kH around the 7.8-8 dKh mark. My Ca 420 and Mg 1230. I dose Triton methods Core 7.

I was away for a week and my pH increased from 8.2-8.3 to 8.3-8.4. The last few days the alkalinity demand seemed to skyrocket from 20ml of 3a&3b Core 7 combined to nearly 40ml, and even then there was a gradual drop of the dKh to 7.6 dKh My tank is lightly stocked with a variety of LPS and SPS corals of small size. No matter what I dosed the demand still seemed to increase. It seemed way too high, and I suspected a problem so cut off all dosing for 2 days. The kH dropped from 7.6 to 6.4dKh.

Previously the tank had been very stable, with a slow gradual increase in 3a&3b usage.

Please help
 
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Joe Batt

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Nope not dosing vinegar I have a very effective thriving fuge. My nitrates are generally very low around 2-5ppm, I haven't checked them but doubt any change in that value.
 

Martin Kuhn

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Most likely that’s good news. Your stone corals start growing faster then before. As a result the calcium carbonate consumption goes up.

Dose more :)
 
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Joe Batt

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Most likely that’s good news. Your stone corals start growing faster then before. As a result the calcium carbonate consumption goes up.

Dose more :)
20ml of both 3a and 3b (40ml daily) seems a huge amount....and to go up so quickly seems strange.
 

Randy Holmes-Farley

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20ml of both 3a and 3b (40ml daily) seems a huge amount....and to go up so quickly seems strange.

Without knowing the tank volume, or much better yet, how much in dKH per day these additions are calculated to boost alk, I can't know whether it is a small addition, or a huge addition.

The drop from 7.6 to 6.4 dKH in 2 days is not particularly unusual, but is hard to gauge as demand drops off fast as the actual alk drops through the 6's.

In general, an increase in demand can be caused by a lot of things, including nutrient and pH changes in the tank, but is not usually a bad thing unless the sand seems to be hardening or some such thing that demonstrates a big increase in calcium carbonate precipitation. Dosing pump changes in dosed amounts also sometimes explain changes, despite the same time being on.
 
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Joe Batt

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Apparently 2ml of 3a&3b increase the dKh by 0.195 in 100 Ltr. My tank is approx 320 litres liquid volume.

Thus I was dosing 20ml per day which equates to 0.61 dKh in my tank. Within a few days it jumped to 40ml equating to 1.22 dKh per day.

The tank has around 35 frags. Mixed LPS SPS with a few half palm sized.
 

Martin Kuhn

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1.2 dKH / day is absolutely typical for SPS stuffed tanks with good growth.
There are even tanks with higher demands.
 

Randy Holmes-Farley

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Apparently 2ml of 3a&3b increase the dKh by 0.195 in 100 Ltr. My tank is approx 320 litres liquid volume.

Thus I was dosing 20ml per day which equates to 0.61 dKh in my tank. Within a few days it jumped to 40ml equating to 1.22 dKh per day.

The tank has around 35 frags. Mixed LPS SPS with a few half palm sized.

That's does not seem excessive to me, and I'd just dose it. Even a soft coral tank can use 2 dKH per day.

Why did it change? Not sure. Might just be more growth for some reason.
 

wiktor

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My alkalinity as suddenly started to drop like a stone, but no sign of precipitation, and dosage goes into good flow area. I don't know why.

I maintain my kH around the 7.8-8 dKh mark. My Ca 420 and Mg 1230. I dose Triton methods Core 7.

I was away for a week and my pH increased from 8.2-8.3 to 8.3-8.4. The last few days the alkalinity demand seemed to skyrocket from 20ml of 3a&3b Core 7 combined to nearly 40ml, and even then there was a gradual drop of the dKh to 7.6 dKh My tank is lightly stocked with a variety of LPS and SPS corals of small size. No matter what I dosed the demand still seemed to increase. It seemed way too high, and I suspected a problem so cut off all dosing for 2 days. The kH dropped from 7.6 to 6.4dKh.

Previously the tank had been very stable, with a slow gradual increase in 3a&3b usage.

Please help
What % water change do you usually do. I have the same issue right now. Suddenly my alk consumption has increased. What i’m doing about it: 30% water change to try naturally restore levels. KH buffer i used yday for 1 day today will be day 2. Enough oxygen in the tank?
 

Randy Holmes-Farley

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What % water change do you usually do. I have the same issue right now. Suddenly my alk consumption has increased. What i’m doing about it: 30% water change to try naturally restore levels. KH buffer i used yday for 1 day today will be day 2. Enough oxygen in the tank?

Why do you ask about O2? I don't know of a reason to associate O2 with alkalinity demand.
 

Randy Holmes-Farley

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i find oxygenating the water helps with stability

What sort of stability? How do you oxygenate water?

If you mean pH stability, the effect is not oxygenation, but equilibration of CO2.
 

wiktor

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What sort of stability? How do you oxygenate water?

If you mean pH stability, the effect is not oxygenation, but equilibration of CO2.
Helps with stabilising your co2 yeah. But i have a packed tank w corals and fish so extra oxygen helps my tank and somehow upped my alk but oh fell a tad.
 

wiktor

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Helps with stabilising your co2 yeah. But i have a packed tank w corals and fish so extra oxygen helps my tank and somehow upped my alk but oh fell a tad.
Now i’ve switched to dosing kh buffer to stabilise ph and alk
 

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