Falling alk, mag rising?

[Waterjockey]

I have a small 30 gallon with mostly lps. I maintain alk and calcium via kalk in my ato. I have (had) a lot of coralline algae, and dosed mag via dosing pump to maintain around 1,400 as I don't do a lot of water changes (awc build in progress).
I have intentionally been slowly letting my alk slide from mid 9's dkh to high 7's/low 8's over the last 3 weeks or so. Calcium had been dropping as expected, and I have been adding calcium to keep it up in the low 400's as I dropped to my new target levels.
Magnesium however, has been climbing...I am at 1/3 the dose I normally ran, and just cut that in half again today. Is this normal and to be expected? (It's now at 1560 as per Red Sea pro). I know a lot of people have had typically high readings with read sea, but I just got a Salifert mag kit as my red Sea kit was nearly depleted, and it confirms (my red Sea reads a little lower than the Salifert...weird).

The only other change over the last month or so, is I added a long spine black Sea urchin, and he/she has eaten about 1/2 the coraline off the back glass already. I was wondering if demand for mag would normally fall as my alk did? Or is this because the urchin has eaten so much of the coralline that my mag demand has dropped.
I honestly did not expect the urchin to grow so fast (almost doube in size already), or be such a voracious eater. I'm afraid I may have to find a new home for it in the next few months as I am beginning to think my tank is going to be too small for him
Any thoughts on rising mag with falling alk?

 

[Nick92515]

Could it be your salt? Have you tested some fresh made saltwater. My salt solidified due to the humidity and I used it, only to find the mag in it was 1800+ I wound test that to attleast rule it out.

 

[Waterjockey]

Could it be your salt? Have you tested some fresh made saltwater. My salt solidified due to the humidity and I used it, only to find the mag in it was 1800+ I wound test that to attleast rule it out.

Thanks, but I know it's not the salt..... I haven't done a waterchange during the alk drop, and I have been watching the mag rise with each test (I test mag once a week). I have been cutting back my mag dosing each week as well.

 

[saltyfilmfolks]

but you have been playing with nutrients correct? that effect alk.

 

[Elementalj]

Probably won't have any algae issues at a level that high. I'd recommend a water change of some sort, and halt the magnesium dosing at least until it returns to a more livable level. I've always understood the uptake of magnesium to be slower anyhow. If you're using classic two part, if also wonder what your salinity is without the WC's.

 

[Waterjockey]

but you have been playing with nutrients correct? that effect alk.

Yes, I was playing with nutrients looking for a "sweet spot". But I have intentionally been dropping alk as well, and think I've found the "sweet spot" for that too. One of the two unhappy corals is happy again, it's too soon to tell if my lobo is happier or not yet

 

[Waterjockey]

Probably won't have any algae issues at a level that high. I'd recommend a water change of some sort, and halt the magnesium dosing at least until it returns to a more livable level. I've always understood the uptake of magnesium to be slower anyhow. If you're using classic two part, if also wonder what your salinity is without the WC's.

Yes, maybe I should just stop mag dosing completely till the level drops.
I don't use 2 part, rock steady at 35ppt

 

[Elementalj]

10-4

 

[saltyfilmfolks]

Yes, I was playing with nutrients looking for a "sweet spot". But I have intentionally been dropping alk as well, and think I've found the "sweet spot" for that too. One of the two unhappy corals is happy again, it's too soon to tell if my lobo is happier or not yet

they are linked, rember .

 

[Waterjockey]

they are linked, rember .

I think that was part of the problem with the lobo and trachy. Dropped nutrients much lower but kept alk in the higher range. The lobo at least looks much better, and everything else looks fine. Hopefully the trachyphyllia will stop wasting away

 

[saltyfilmfolks]

I think that was part of the problem with the lobo and trachy. Dropped nutrients much lower but kept alk in the higher range. The lobo at least looks much better, and everything else looks fine. Hopefully the trachyphyllia will stop wasting away

you dropped the nutrients (and alk) and used something else like kalk as a buffer to increase alk?

 

[Elementalj]

you dropped the nutrients (and alk) and used something else like kalk as a buffer to increase alk?

I would only use kalk to maintain alkalinity, it's not very reliable for increases.

 

[saltyfilmfolks]

I would only use kalk to maintain alkalinity, it's not very reliable for increases.

understood and agreed.
just wondering his method.

 

[Waterjockey]

you dropped the nutrients (and alk) and used something else like kalk as a buffer to increase alk?

No. I use kalk in my ato to maintain alk and calcium. Have for sometime. I don't use any 2 or 3 part...just kalk. Used to maintain about 9.5 alk, and higher nutrients. Dropped nutrients to current levels some months ago. Began dropping alk over the last 3 weeks or so from 9.5 to currently about 8.0. My tank appears pretty happy for the most part with my current levels of nutrients and alk.
I was just wondering if it was normal for mag to rise relative to a lowering alk. Alk dropped, but mag began to rise as I dropped the alk. Was just wondering why?

 

[Elementalj]

No. I use kalk in my ato to maintain alk and calcium. Have for sometime. I don't use any 2 or 3 part...just kalk. Used to maintain about 9.5 alk, and higher nutrients. Dropped nutrients to current levels some months ago. Began dropping alk over the last 3 weeks or so from 9.5 to currently about 8.0. My tank appears pretty happy for the most part with my current levels of nutrients and alk.
I was just wondering if it was normal for mag to rise relative to a lowering alk. Alk dropped, but mag began to rise as I dropped the alk. Was just wondering why?

Ok, here's a good question. What brand of kalkwasser are you using? I have been using Brightwell's kalk+2 which has a little magnesium and strontium in the mix.

 

[Randy Holmes-Farley]

If you are not adding magnesium, or using tap water, I would not worry about magnesium apparently rising. It likely is not.

FWIW, the kalk+2 is not going to add any useful amount of magnesium. It's an incredibly poorly designed product. It has hardly any magnesium (less than my "pure" calcium oxide did when I tested it for impurities) and it doesn't dissolve into limewater anyway.

 

[Waterjockey]

Ok, here's a good question. What brand of kalkwasser are you using? I have been using Brightwell's kalk+2 which has a little magnesium and strontium in the mix.

I use Seachem kalk powder, simply because that is what is available locally. For the amount I use it is economical. Same with the mag, Seachem again. The kalk lasts me six months or more, the mag probaby a year or so

 

[Waterjockey]

If you are not adding magnesium, or using tap water, I would not worry about magnesium apparently rising. It likely is not.

FWIW, the kalk+2 is not going to add any useful amount of magnesium. It's an incredibly poorly designed product. It has hardly any magnesium (less than my "pure" calcium oxide did when I tested it for impurities) and it doesn't dissolve into limewater anyway.

Thanks Randy. I had mag on a maintenance dose which kept the levels pretty flat. I originally did not stop dosing mag while I let the alk slide, and instead of staying flat, mag rose week after week. Just wondered of that was normal.

 

[Elementalj]

If you are not adding magnesium, or using tap water, I would not worry about magnesium apparently rising. It likely is not.

FWIW, the kalk+2 is not going to add any useful amount of magnesium. It's an incredibly poorly designed product. It has hardly any magnesium (less than my "pure" calcium oxide did when I tested it for impurities) and it doesn't dissolve into limewater anyway.

Thanks for the info, I'll switch as soon as the ATO is empty. [emoji41]
Being completely frank, everything seems to be doing great though!