High Magnesium - 1700+

[chatyak]

Tested Reef Crystals at 1.0255 (half way between 1.025 and 1.026) @ 75 F degrees.

Ca: 535
dKH: 11
MG: 1710

MG is rather high isn't it? I don't want my snails to die as I have heard high MG can cause them to waste away...


With that said - I do like the parameters and I understand the MG should be roughly 3x the CA levels and it helps to stabilize PH levels... will it be okay as long as it is done slowly? My entire tank is using Tropic Marin Pro Reef at the moment and it sucked parameter wise. Never buying it again. I changed out 5 gallons (140 gallon total volume roughly)... the issue is I don't want to shock the sytem... currently my alk is around 6 from using TMP and I dont want the sudden blast of of a dKH of 11, and the magnesium issue.

[chatyak]

I tested again. MG came to 1560... not sure why the difference... Regardless even if its at 1560 - will this affect my fighting conch and turbo snails?

[bertoni]

1560 ppm should be fine. People run tanks at significantly higher levels without problems.

[chatyak]

1560 ppm should be fine. People run tanks at significantly higher levels without problems.

I could have sworn bertoni I just read an archived post of you saying that snails would suffer at higher ppm.... good to know about the 1560 though. Would you say the same at 1700 as well? I'm changing about 10 gallons of water per day... to switch the tank over from tropic marin's low reading to reef crystals.... it shoudln't shock the tank I don't think? :uhoh2:

[Randy Holmes-Farley]

It also may not be an accurate magnesium result, or the salinity is higher than you think. :)

[chatyak]

It also may not be an accurate magnesium result, or the salinity is higher than you think. :)

I calibrated my refractometer with a 35ppt solution. :bounce3:

I will test a 3rd time today and see what it says.

[chatyak]

I tested 2 more times today. They were roughly 1510 - 1570 respectively.

So I have 3 readings between 1500-1570 and the 1st result was 1710. Odd.


Salinity was just a sliver above 1.025

[bertoni]

The 1500-1570 spread seems reasonable to me, given test kit issues and so on. I'd pick a random number between the limits. :)

[chatyak]

The 1500-1570 spread seems reasonable to me, given test kit issues and so on. I'd pick a random number between the limits. :)

Will a large water change affect things or should I do minor changes over time so as not to shock with the higher dKH and MG etc.. Also - do you think my snails will be okay with MG at that level? I dont know why the test kit showed 1700+ the other time. I'll test again tomorrow to be sure.

[Randy Holmes-Farley]

I would just do regular changes over time. That magnesium level doesn't warrant unusual actions, IMO.

[antbreon]

if you are changing water and the water you are adding has high..mag..the water you are removing and adding it to is lower so it will blend and average out..as long at the mag in your tank stay in parameters ..i wouldn't worry..

[JustAClownFish]

I have the same problem. I use IO at 1.026. Just tested and it's beyond 1700ppm. Is there any way to get this down? I just did a couple water changes last week because I had problems with high mg due to the red sea pro salt mix. I didn't expect to have the same problems with IO.

[karimwassef]

doesn't really do any harm. plenty of threads on it.

[bertoni]

The only practical to lower the magnesium level is water changes with a lower-magnesium salt. I'd probably just ignore the issue.

[JustAClownFish]

I read that inverts struggle with high mg and that some corals might not color up as nicely.

[bertoni]

Maybe. I have gotten conflicting reports on that, and I am no longer sure that invertebrates will have problems. Coral coloration is a very difficult subject, and I don't know what the effect, if any, might be, but I haven't heard much negative information.

[orcafood]

Ime high magnesium raises the caco3 precipitation point. Not bad but calcifying organisms wont grow as quickly, or at all. Especially if ca is low.

Over all do water changes with a lower mg salt blend. Instant ocean is how I usually drop parameters if need be :)

[mcgyvr]

Seems to be quite a few reports of inconsistencies with Instant Ocean lately (both regular and RC)..
Not sure if its all just measurement error or maybe time to jump ship..

[bertoni]

Adding magnesium will tend to drop the rate of abiotic precipitation because magnesium fouls crystals as they form. That's one of the reasons that saltwater can be supersaturated with respect to calcium carbonate.

[orcafood]

Interesting I just made 100 gall of IO and it tested perfectly for the big 3

[JustAClownFish]

I don't know if the error is on my side. I always have problems with high Mg and sometimes Ca no matter what salt mix I use. I purchased the normal red sea salt mix yesterday. Just mixed a bucket.

They claim for 35ppt:

Ca 430
Mg1280
alk 8

I measured (except for Ca, need a new test kit)

Mg 1500
Alk 9.6

I measured a couple times with Salifert test kits. It's always high. The salinity I triple checked with the Red Sea refractometer. It's exactly 35ppt.

When I use the Coral Pro salt mix I get Mg beyond 1700ppm, Ca around 550, alk 12 -13dkh.

[bertoni]

Has the refractometer been tested with a calibration solution? The PinPoint salinity calibration will work, and it's cheap. You can make a calibration solution, too:

http://reefkeeping.com/issues/2004-06/rhf/index.htm

I suspect the issue is a bad batch of salt, though.

[five.five-six]

Magnesium sulfate has a much higher refractive index than sodium chloride. You should double check your salinity with a hydrometer.

[JustAClownFish]

I have the calibrating solution. It's def. a problem on my side. I calibrate, test the water, and then when I test again it's off. So I don't really know whether the first measurement I took is the accurate one or the second.

@five.five-six

What do you mean by Magnesium sulfate has a higher refractive index than sodium chloride?

[bertoni]

A solution that has a large amount of magnesium sulfate in it might have a different refractive index than saltwater, causing it to read inaccurately, but the difference between 1500 ppm and 1275 ppm is too small to have an effect, whether the magnesium is from magnesium chloride or magnesium sulfate.

I'd go with the 1500 ppm measurement, but maybe a local fish store could run a check for you.

[JustAClownFish]

I work at a reef store. I measured my water a couple times with different test kits. I'll aim for a lower sg until my tank is fully stocked. This should, over time, get the Mg down.

[chungsl]

Adding magnesium will tend to drop the rate of abiotic precipitation because magnesium fouls crystals as they form. That's one of the reasons that saltwater can be supersaturated with respect to calcium carbonate.

my tank saltwater's magnesium is 1550ppm because of dosing epsom salts water. Now there are some calcium carbonate "stone" formed on the surface of sand bed.

[bertoni]

I'll aim for a lower sg until my tank is fully stocked.
I suspect that a low SG could more harmful than a high magnesium level. I think that keeping the SG at no less than 1.025 is a good idea, although people are successful with somewhat lower levels.

[karimwassef]

From personal experience- maintaining a high Mg, Ca and Alk allowed my corals to survive even as my salinity dipped to 1.019... they weren't happy but they didn't die either.

[tmz]

fwiw. I've run my tanks for years at around 1500 to 1550 ppm for years without discernible negative effects on stony coral growth or inverts ; but a noticeable lack of abiotic calcium carbonate precipitation than at lower levels which I consider a plus.

[JustAClownFish]

I suspect that a low SG could more harmful than a high magnesium level. I think that keeping the SG at no less than 1.025 is a good idea, although people are successful with somewhat lower levels.

I shoot for 1.024 so I have some wiggle room. If I don't top off my tank it'll go up to 1.026 in a matter of two days. Given that it should be fine. Before I mixed my water at around 1.026. Also, I don't want my alkalinity to skyrocket. When I used the coral pro salt mix I easily hit 13 dkh. I have no stony corals in my tank except a few tiny frog spawns and one hammer.

[tmz]

1.026 is best, IMO; it's the average for seawater. Note, all animals rely on an internal sg to maintain live sustaining biochemical activity. Invertebrates can't osmo regulate like fish can by drinking and urinating and via their kidney functions; so ,for the animals like corals that don't osmoregulate their internal salinity is highly dependent on the surrounding water;if it's saltier than their internal sg they will loose fluids like a pickle; if it's lower it will flow into them and lower their internal sg. Either way it messes up their homeostasis which is necessary for life .

[JustAClownFish]

Yesterday I measured 1.025 so I can safely assume that it's going to be 1.026 by tonight due to evaporation.