Why is my tank consuming mg and kh but not ca

[Raj]

May 21 reading

Mg 1350 after I added BRS mg mix it was 1200 before

Ca 400

Kh 9

Ph 8.3

 

May 26 reading

Mg 1200

Ca 400

Kh 6.4

Ph 8.3

 

Salifert test kit

 

About my system

95 gallon tank + sump

Around 80 lbs of live rock

Added 5 lbs of dry rock 2 weeks ago

1 mp40 + 1 mp10 @ 40%

2 ecotech 30s @ 60% max for 4 hrs on 12 hr light cycle

 

Corals

Mix of mushroom, tons of paly, Zoa, colony of xenia, 2 frags of bird nest 2 more sps don't know the name 6 frag of acan

2 frag of bird of paradise, 5 frag of Monti

 

 

All live stock are doing ok (surviving) but not thriving

 

IO regular salt

 

I only add mg when needed

Change water 2 times a month and run gfo and carbon on BRS reactor.

 

 

I have had this system running for last 8 month

 

I have noticed this for quiet a long time but don't know what's the reason I have even seen the Ca go up sometime

 

Testing after lights go out at the same time

 

Please help nail down this issue !!!

 

 

 

 

 

 

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[AlanM]

I had the same thing happen to me for a long time.  It turned out that water changes were able to keep up with the Ca consumption, but not the alkalinity.  The typical carbonate ion concentration is around a factor of 2 or 3 lower than the Ca ion concentration (at least in my tank it is) and it gets used by more things in the tank than just the calcification of corals.  Bacteria use it as well and so does algae growth.  So you'll probably always use more alk than Ca.  

 

Once you get lots of hard corals growing in there or lots of coralline algae you'll start to see Ca dropping instead of your water changes keeping up with it.

[Raj]

I had the same thing happen to me for a long time. It turned out that water changes were able to keep up with the Ca consumption, but not the alkalinity. The typical carbonate ion concentration is around a factor of 2 or 3 lower than the Ca ion concentration (at least in my tank it is) and it gets used by more things in the tank than just the calcification of corals. Bacteria use it as well and so does algae growth. So you'll probably always use more alk than Ca.

 

Once you get lots of hard corals growing in there or lots of coralline algae you'll start to see Ca dropping instead of your water changes keeping up with it.

Thanks for the tip AlanM

 

So do you suggest to do more frequent water changes or start adding Kh and Mg as needed on daily basis ?

 

 

 

 

 

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[Raj]

I had the same thing happen to me for a long time. It turned out that water changes were able to keep up with the Ca consumption, but not the alkalinity. The typical carbonate ion concentration is around a factor of 2 or 3 lower than the Ca ion concentration (at least in my tank it is) and it gets used by more things in the tank than just the calcification of corals. Bacteria use it as well and so does algae growth. So you'll probably always use more alk than Ca.

 

Once you get lots of hard corals growing in there or lots of coralline algae you'll start to see Ca dropping instead of your water changes keeping up with it.

I see the answer to my question ." Keep up with it " thanks again AlanM

 

Happy weekend

 

 

 

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[AlanM]

I would absolutely start dosing alkalinity solution.  Buy some of the sodium carbonate from BRS or a local fish store, mix it up into a gallon jug of RO/DI, use the calculator on BRS to figure out how much to add to bring it up to your target level after you test.  Then test again in a few days and calculate how much solution to add again.  Then you'll know the daily dose.  Do that for a while and test once a week or so to see if it's all holding steady.   For what it's worth, I keep mine at 3meq/l which is 150ppm or 8.4dkh.  I don't use dkh because I like the even numbers of 3 or 150.

 

If you have a pH meter that records data it can give you an idea that it's happening if you see the diurnal peak and valley dropping, but the raw number doesn't tell you much.

[WheresTheReef]

I'm not an expert in this area, but wouldn't you want to use Sodium Bicarbonate if trying to raise alkalinity faster? I believe Sodium Carbonate will also have a significant effect on the pH. Either way, I would raise alkalinity slowly or your corals will have more issues.

[Raj]

I would absolutely start dosing alkalinity solution. Buy some of the sodium carbonate from BRS or a local fish store, mix it up into a gallon jug of RO/DI, use the calculator on BRS to figure out how much to add to bring it up to your target level after you test. Then test again in a few days and calculate how much solution to add again. Then you'll know the daily dose. Do that for a while and test once a week or so to see if it's all holding steady. For what it's worth, I keep mine at 3meq/l which is 150ppm or 8.4dkh. I don't use dkh because I like the even numbers of 3 or 150.

 

If you have a pH meter that records data it can give you an idea that it's happening if you see the diurnal peak and valley dropping, but the raw number doesn't tell you much.

 

I will order some from BRS tonight and will keep my eyes on ph. I have a reef keeper elite but did not calibrate the ph for 6 mth now but I think the reading is somewhat accurate.

 

Btw I have a small bottle of Reef Builder from Seachem .. which is for raising carbonate Alkalinity any harm on using that instead for raising Kh ??

 

 

 

 

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[Raj]

I'm not an expert in this area, but wouldn't you want to use Sodium Bicarbonate if trying to raise alkalinity faster? I believe Sodium Carbonate will also have a significant effect on the pH. Either way, I would raise alkalinity slowly or your corals will have more issues.

I have a reef builder and reef buffer form Seachem

One is to reef builder raise Kh without raising ph and other is to raise both ph and Kh

 

But it seems reefbuilder has both carbonate and bicarbonate .. bottle for reef buffer does not say what it has weard ...

 

 

 

 

 

 

 

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[AlanM]

I'm not an expert in this area, but wouldn't you want to use Sodium Bicarbonate if trying to raise alkalinity faster? I believe Sodium Carbonate will also have a significant effect on the pH. Either way, I would raise alkalinity slowly or your corals will have more issues.

 

Bicarbonate isn't as soluble in water, so it takes twice as much of the end solution to raise carbonate ions the same amount.  Either will have an effect on the pH, but it's true in the short term they do different things.  Either are fine for adding alkalinity, and bicarbonate (Baking soda) is probably easier to get since you don't have to order it from BRS.  Just from grocery store.

[gmerek2]

Everyone did a great job with the alk. Now as far as the magnesium I don't think it should have dropped that fast. It's probably just inconsistency in the testing units. they aren't perfect but as far as mag goes, I just want to know if it's low, medium or high. Mag has a pretty wide acceptable range and usually can be replaced with regular water changes. I didn't have to start dosing it until the sps started to fill in the tank

[WheresTheReef]

Yea I agree want to get mg up to 1320-1350 range to avoid precipitation. Mine always goes down with water changes even when using reef crystals.

[Raj]

Everyone did a great job with the alk. Now as far as the magnesium I don't think it should have dropped that fast. It's probably just inconsistency in the testing units. they aren't perfect but as far as mag goes, I just want to know if it's low, medium or high. Mag has a pretty wide acceptable range and usually can be replaced with regular water changes. I didn't have to start dosing it until the sps started to fill in the tank

 

I prepared another batch of BRS mg mix will raise it to 1300-1350..

 

Test kit should be correct since this is not the first time I have seen it depleted quick ..

 

 

 

 

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[gmerek2]

You have an auto top off right? No salinity fluctuation

[Raj]

Yes I have a ATO

 

 

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[Raj]

You have an auto top off right? No salinity fluctuation

 

Yes I have always have had ATO since day one .. salinity never fluctuates ...

 

But I'll have to monitor salinity when I dose mg

 

 

 

 

 

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[Origami]

The magnesium depletion is unusual.

 

Do you have a kalk reactor?

[Raj]

The magnesium depletion is unusual.

 

Do you have a kalk reactor?

 

I am not adding anything anything

 

I do siphon sand when I take the water out though .. not sure of that has anything to do with mg depletion

 

I did water change day before and check my mg it was 1260 I'll check today see if went down or stayed there ..

 

 

 

 

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[Origami]

Do that.

 

Salt water thru a kalk reactor (which is the wrong way to configure one) can rapidly deplete magnesium while failing to add alkalinity. That's why I asked.

 

Take your water samples before stirring up the water to make sure that they're clear. Run a test multiple times if the test result is unexpected. This helps to mitigate variance from your procedure.

 

Mg depleting so quickly points to either a test error or precipitation. Typically, because the magnesium ion is so light compared to the weight of two chloride ions, it takes a whole lot of magnesium chloride to raise magnesium by very much. How large is your tank and what did you use (and how much) to raise your mag level?

 

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[Raj]

Do that.

 

Salt water thru a kalk reactor (which is the wrong way to configure one) can rapidly deplete magnesium while failing to add alkalinity. That's why I asked.

 

Take your water samples before stirring up the water to make sure that they're clear. Run a test multiple times if the test result is unexpected. This helps to mitigate variance from your procedure.

 

Mg depleting so quickly points to either a test error or precipitation. Typically, because the magnesium ion is so light compared to the weight of two chloride ions, it takes a whole lot of magnesium chloride to raise magnesium by very much. How large is your tank and what did you use (and how much) to raise your mag level?

 

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Hi Origami,

 

I have a 75G tank + 20 G sump - 20 G for rocks I guess so water volume should be around 75 G.

 

I mixed 7.25 cups of Mag Chloride + .75 cup of Mag sulfate to make the BRS Mag Mix -- and I normally dose after waiting a day of water change.. to get to Mag to 1300 to 1350 ppm 

I did water change Saturday and Saturday night reading was

Mag 1260

Kh 7.6

Ca 400

No3 10.0 ppm (working on fixing this with GFO and Carbon -- Skimmer -- frequent socks change)

 

I will dose Mag and Kh as advised by AlanM tonight

[gmerek2]

My magnesium test is so inaccurate. It's hard to explain. It basically says low medium or high. But again that's all we need to know. I know it breaks numbers down like that but it only takes 2ml of tank water. My alk test takes 10ML. So the 150 difference you are seeing could be a million different factors. Did the moisture left over in the test tube cause the missing? Were you looking at the test glass under a different color light? Did you push harder on the plunger to get that last drop? Was there microscopic bubbles in the test this time? Were there a couple extra powder grains in the fun dip powder that gets dumped in with the tiny spoon? The two different drop containers.....did you use a protractor to make sure they were 90 degrees upright to make uniform size drops? Did you fill to the top middle or end of the 2ml line both times? I could go on and on but the meaning of the story is they aren't accurate measuring devices. And the fluctuation you are seeing Isn't much.

[Origami]

How much of the BRS Mag Mix do you use? All of it every water change? How much mix does the 8 cups of dry make? Or do you just dose it dry? And, if dosed dry, do you dump it in all at once or sprinkle some and allow it to dissolve before adding more?

 

I don't recall my magnesium tests varying by 150 ppm but, then again, it's not something that I test very often. (I use Seachem, not Salifert, for my magnesium testing.)

 

Mg of 1250 should easily allow you to supersaturate the water column with typical levels of calcium and alkalinity used in this hobby. There's no need to go to really high levels unless you're after something else. (Some folks used to run it up to 1500 to knock out bryopsis, but it was unclear if it was the magnesium or some impurity that was doing this.) Of course, there's no known harm in taking it up to 1350 either.

 

As for your alk consumption, it doesn't take much in the way of hard coral growth to drop alk rather quickly. It's a little known fact, though, that alkalinity can drop by more than the typical ratio of 2.8 dKH for every 20 ppm of calcium if the aquarist is using water changes to manage elevated nitrates. In this case, the aquarist would only see a 10 ppm decline in calcium for every 2.8 dKH of alkalinity drop. And, because the drop in calcium is so low and within the resolution error of the test kit, it's often missed by the aquarist. Of course, the same can be true if trying to resolve 20 ppm of drop in calcium.

[Raj]

My magnesium test is so inaccurate. It's hard to explain. It basically says low medium or high. But again that's all we need to know. I know it breaks numbers down like that but it only takes 2ml of tank water. My alk test takes 10ML. So the 150 difference you are seeing could be a million different factors. Did the moisture left over in the test tube cause the missing? Were you looking at the test glass under a different color light? Did you push harder on the plunger to get that last drop? Was there microscopic bubbles in the test this time? Were there a couple extra powder grains in the fun dip powder that gets dumped in with the tiny spoon? The two different drop containers.....did you use a protractor to make sure they were 90 degrees upright to make uniform size drops? Did you fill to the top middle or end of the 2ml line both times? I could go on and on but the meaning of the story is they aren't accurate measuring devices. And the fluctuation you are seeing Isn't much.

 

I know there are micro bubbles in my tank Noticed it was coming from the skimmer .. will fix that tomorrow .. sample will have some for sure also I noticed I do not rinse the cup that I take the water out of tank after use, noticed it today.

 

From now like the other Master Reefer's have suggested I would take at least 2 test for each test just to double check the number ...

 

 

 

 

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