kalk causes phosphate, mg precipitation?

[Sk8r]

I've heard this from several sources. I run a kalk reactor. I was told that if I put the kalk drip tube over the skimmer intake it may make the skimmer suck up phosphate that may precipitate out as the kalk hits the water. My tank phosphate is falling, but I have a lot of other circumstances [like a big refugium] that may be helping that.

Question 2: magnesium precipitation? Otherwise higher mg consumption? Where's it going? My lfs owner, a reefer of long experience, handed me a big bottle of Kent Magnesium and said I'd find it got used faster: since my first Tech M bottle [small] has lasted me for 2 years and I now am actually having to add mg, something is going on, but what?

Before we get another reefing 'urban legend' started, and it's my fault, can we have the chemists' take on this?

Just checking at the source. TIA.

[Mike O'Brien]

Magnesium and Phosphate both bind to growing calcium carbonate crystals. Since adding limewater does facilitate the precipitation of calcium carbonate the P and Mg may be reduced slightly. Also there is little to no Mg in limewater, so the import would be much less that the export from calcification be it biotic or abiotic.

[bertoni]

I don't know of any mechanism that would cause kalk to add phosphate. Phosphate tends to precipitate out of limewater due to the high pH. Limewater might help reduce phosphate levels in the tank:

http://www.reefkeeping.com/issues/20...f/index.php#15

That's not really been demonstrated, though.

Limewater can increase the rate of calcification in the tank by improving water conditions. Unlike B-Ionic, the DIY 2-part, and many other supplements, limewater does not add magnesium to the water. Magnesium is consumed along with calcium and alkalinity as corals and coralline algae deposit their skeletons and other structures:

http://www.advancedaquarist.com/issues/oct2003/chem.htm

So an increase in calcification is going to cause an increase in magnesium consumption. It's possible that using limewater might cause preferential consumption of magnesium, but I don't know of any evidence that it does. Dosing limewater shouldn't cause abiotic precipitation of magnesium, assuming it's not overdosed.

I suspect the preceived added magnesium consumption is mostly more calcification and less magnesium from other supplements.

[Sk8r]

Ah. My title: bad comma. Hence the question as to what I meant. And I make my living with words.

I meant---which you answered---does kalk cause phosphate to precip out? Does it cause mg to precip out? So the answer is---yes on the first question; on the second question, more likely the corals are using more and none is coming in from the supplementation.

[bertoni]

Kalk can cause phosphate impurities to precipitate when it's added to RO-DI water. Whether it lowers phosphate in saltwater or not isn't known.

[Sk8r]

Got you. THanks, Bertoni, for that clarification.

[bertoni]

You're welcome! Let us know how the Mg consumption shapes up.

[Sk8r]

LEt's say I've had a small bottle of Tech-M forever, like 2 years. I'm running through that at the rate of 2 doses every month and a half. My lfs [experienced reefer] gave me a big bottle of MG and said I'd need it. My corals really suffered in the move ---rock accidentally cooked, and I had to put sps into a raw 'new' tank, but they're starting to perk, and I just had to add more mg.

Meanwhile my longterm algae nightmare [caulerpa in main tank] fought off the 20 g fuge in April, May, and June, but now is dying out, since I added the kalk reactor in late June. I'm now down to one 1/2 inch sprig that looks unhealthy. So both things ARE coming true, in the too-good-to-be-true dept., but I'm wondering is it time, is it the fuge, is it because it's precipitating and getting sucked up in the skimmer? I'm not complaining, understand!

Here's hoping!

[Billybeau1]

Almost sounds to me like a microalgae problem. Do you know what your PO4 level is ?