What is going on with my ALK?

Defect

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So I have no idea what is going on with my alk here. I am trying to drop my alk and I havent dosed since the 22nd and my alk test is saying it is the same as it was. 10.4 alk...to high for my liking so I am dropping it down closer to 9.....or atleast trying to. I have read that your calcium should be used up almost just as much as alk....true? I am dosing 10 ml of calcium a day and my calcium is staying at 410. Mag is testing at 1400. Any ideas?

Thanks
 

Randy Holmes-Farley

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Can you describe what is in the tank?

Calcium and alkalinity are used in a specific ratio, and I don't want to give that ratio just now since it is today's Reef Chemistry question of the day:

https://www.reef2reef.com/forums/re...istry-question-day-70-calcium-alkalinity.html

but I will say that you always notice the drop in alkalinity before you notice the drop in calcium, in part because there is effectively 5 times as much calcium already in seawater than there is "alkalinity".

So if alk is not dropping much, calcium won't either.

It is not surprising that the drop is slow in many aquaria, but it all depends on how fast your hard corals (if any) and coralline algae are growing.

It will eventually drop and 10.4 dKH is not any sort of problem (unless this is a ULNS SPS system), so patience is called for. :)
 

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My ALK is 12dkh and CA is 600ppm. PH 8.0 Is there a problem,if so what sholud I do? I have SPS,LPS and fish.
 
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Randy Holmes-Farley

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Can you describe what is in the tank?

Calcium and alkalinity are used in a specific ratio, and I don't want to give that ratio just now since it is today's Reef Chemistry question of the day:

https://www.reef2reef.com/forums/re...istry-question-day-70-calcium-alkalinity.html

but I will say that you always notice the drop in alkalinity before you notice the drop in calcium, in part because there is effectively 5 times as much calcium already in seawater than there is "alkalinity".

So if alk is not dropping much, calcium won't either.

It is not surprising that the drop is slow in many aquaria, but it all depends on how fast your hard corals (if any) and coralline algae are growing.

It will eventually drop and 10.4 dKH is not any sort of problem (unless this is a ULNS SPS system), so patience is called for. :)

My tank is 90% sps frags 10% LPS.

I am really confused about whats going on. I have noticed a significant decrease in coralline algae growing. It used to grow like crazy and now it has seem to just have stopped. My frag rack used to get coralline growing on it in a matter of weeks now its been in my tank for over a month with not one hint of coralline growing. Frags are not growing either.

I dont think its nutrients. I have tested my p04 8 times in the past week and always comes out 0.00. My nitrates are sitting ~5. Not sure whats happening. Only thing that I have changed in my system is I started passive carbon in my sump.
 
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So what would cause a reef tank to not take up any alk? Is the non existant p04 causing any problems?
 

Randy Holmes-Farley

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So what would cause a reef tank to not take up any alk? Is the non existant p04 causing any problems?

Not many calcifying organisms, or poor growth from those that are present.

Low phosphate isn't generally a problem for calcification, unless you have pushed it very low with a lot of a binder like GFO.
 
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Not many calcifying organisms, or poor growth from those that are present.

Low phosphate isn't generally a problem for calcification, unless you have pushed it very low with a lot of a binder like GFO.

So now to try and figure out why there is no growth going on.

I guess I should take the carbon out of the sump. Didn't think it would do much to the tank as far as growth, skim less wet, do a 20% water change and stop carbon dosing? Was only dosing .4 ml of vodka and didn't dose this morning.

Would you have any recommendations?

Thanks,

Aaron
 
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Yes. Trying to figure out why the vodka dosing would cause this though.
 
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I have low nutrients with alk around 10. Sps wasn't looking so hot, dropped alk to 8 and they have responded very well. Growth took off and colors look better too.
 
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Sorry to bring this back up but I thought I read somewhere that if you have higher calcium it lowers the alk level in your tank...is this correct? My calcium is testing out at ~390. My tank had a growth spurt for a while and now I have been upping my calcium dosing but it doesnt seem to be moving up and lost the rapid growth I was getting along with my coralline at the stand still. I had calcium running at 450 previously and was getting massive amount of coralline growing. Should I just keep upping the dosage of calcium until it gets to 450 and then level my alk off at 8.5 where I want to keep it?

Might this be the reason for my alk going up and calcium going down? Hope the question makes sense....
 

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Raising calcium doesn't really drive down alkalinity unless it is super high, high enough to really drive abiotic precipitation of calcium carbonate.

The growth of most corals is not much impacted by calcium levels above 380 ppm as it seems to not be the limiting factor in coral calcification unless it is lower than about 360 ppm. :)

That said, raising the calcium to 450 ppm is a fine thing to try if you think it might spur growth. :)
 
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