Does kalkwasser affect magnesium?

[spreston]

I have been dosing kalk for around 3 months. I only dose 7 hours at night, via a dyi kalk reactor with IV drip feed through a overhead ro/di storage tank controlled by a solenoid on a timer. Since I started dosing kalk my calcium has been steady, as well my alk has been steady.

Since I started using kalk (kent kalwasser), my magnesium has been a constant battle. I test weekly for mag and it is usually around 1250, but has been lower. To even maintain it around 1250 which I know should be around 1350, I am having to add 250ml of kent tech-m per week, which seems like alot.

Is this normal?

Also, I have corraline all over the back and side glass, could this be some of the problem?

Ph 8.2
calcium 440
alk 3.25 meq/l
sg 1.025

ps -I recently switched salts from RC to topic marine pro, probably not helping since TM is supposed to be lower in mag.

[JetCat USA]

http://www.advancedaquarist.com/issues/dec2003/chem.htm

[spreston]

Thanks, I have read the article although I don't know if I understand half of it. However, as stated in the third paragraph, it is unlikely that limewater would cause much precipitation of magnesium, rather the depletion was caused by calcification of corals.

I only have a 5 sps's most not more than frags, a dozed lps's and a small crocea. The tank has been setup for 9 months and I wanted it perfect before diving to deep into sps's, but with the magnesium maybe being depleted by no more than I have now, I am nervous about going full blown sps tank.

This is the reason I might think that the corraline is the problem.

[Justin74]

Im having my own problems understanding the material and theory behind some stuff as well.

But on that part how I understood it to be is because the Mg is depleted through calcification, it will need to be supplemented to maintain appropriate levels. Not that using kalk somehow drains the system of Mg by its very use, but through calcification. I think emphasis was put on this element because of the amount of Mg actually in kalk, but due to the high pH of the kalk sollution it leaves the Mg to precipitate to the bottom of the sollution, in turn making the Mg in the kalk sollution basically unavailable.

Someone please correct me if Im wrong or skewed anything.

-Justin

[Ninong]

Limewater (Kalkwasser) does not affect magnesium. That means that if you use limewater, you will have to monitor your magnesium levels and add a magnesium supplement as necessary. A lot will depend on how often you perform water changes and whether your salt mix is low in Mg to begin with.

I suggest testing your freshly made up saltwater to see if it's close to 1300 ppm or much lower than that. You should also test your tankwater for Mg at least monthly if you are using limewater for calcium and alkalinity maintenance.

I have found that using limewater and doing water changes only every couple of months, it's necessary to dose magnesium chloride on a fairly regular basis. This is to be expected.

:D