kH, Ca & Mg Dosing help

[WTJReef]

Hi Guys,

I've been testing my tank water for about a week and have recently introduced my first batch of coral - 4 small LPS frags along with a small Zoa frag into my tank this weekend.

In the week leading up, I was told my Calcium was low by my LFS after I took my water in double check my readings. They were

Mg 1380
Ca 405
kH 9.2
Salinity 1.025

I dosed Ca and saw my kH drop to near 7 and spent the week bringing up kH.

Prior to introducing my new corals I performed some maintenance including a 10% water change.

Its now been 24 hr, my lights are set to acclimation mode and the corals are looking reasonably happy from what I can tell and have recovered from the Dip I did and transport - All Polyps took only an hour or 2 to open back up and have remained open, looking colourful without any mucous secretions

My concern is that my Magnesium appears to be creeping up upon testing again today my (own) readings were:

Mg 1500
Ca 440
kH 8.4
Salinity 1.028

Im using the red sea foundation titration test kits and a Refractometer.

I'd like to see my Magnesium lower, but have been told as long as Calcium is 1/3 the Magnesium then the correct Ionic ratio is present (i.e. my Calcium should be 500) and I'd like my kH around 9-10. Should I be worried?

I have refrained from water change/dosing until I get some advice here. What would you advise as the best course of action?

 

[neonreef3d]

looks like your salinity is a bit high… I would do a small water change to adjust that down to .025 And at the same time you will drop some of your magnesium as well. Depending on what your daily intake is, just dose your alk and ca, adjust your mag once a month or so, depending on the depletion rate…

I found refractometer to be inaccurate, so I use a tropical marine precision hydrometer, and according to that, I would calibrate my Hanna digital hydrometer..

what is the size of your tank.

calcium should be fine at 450, and alk should be at 8-9 dkh. Magnesium at 1300.

 

[Randy Holmes-Farley]

I'd like to see my Magnesium lower, but have been told as long as Calcium is 1/3 the Magnesium then the correct Ionic ratio is present (i.e. my Calcium should be 500) and I'd like my kH around 9-10. Should I be worried?

Another situation where ratios are totally inappropriate.

I cannot even think of a reef situation where optimal levels are not far better considered in absolute terms rather than as a ratio to some other ions, despite many trendy ideas to the contrary.

Just because magnesium is too high or too low, is that a reason to do the same to calcium?

NO.

Calcium is fine at 400-550 ppm, regardless of the magnesium level.

 

[Rmckoy]

Hi Guys,

I've been testing my tank water for about a week and have recently introduced my first batch of coral - 4 small LPS frags along with a small Zoa frag into my tank this weekend.

In the week leading up, I was told my Calcium was low by my LFS after I took my water in double check my readings. They were

Mg 1380
Ca 405
kH 9.2
Salinity 1.025

I dosed Ca and saw my kH drop to near 7 and spent the week bringing up kH.

Prior to introducing my new corals I performed some maintenance including a 10% water change.

Its now been 24 hr, my lights are set to acclimation mode and the corals are looking reasonably happy from what I can tell and have recovered from the Dip I did and transport - All Polyps took only an hour or 2 to open back up and have remained open, looking colourful without any mucous secretions

My concern is that my Magnesium appears to be creeping up upon testing again today my (own) readings were:

Mg 1500
Ca 440
kH 8.4
Salinity 1.028

Im using the red sea foundation titration test kits and a Refractometer.

I'd like to see my Magnesium lower, but have been told as long as Calcium is 1/3 the Magnesium then the correct Ionic ratio is present (i.e. my Calcium should be 500) and I'd like my kH around 9-10. Should I be worried?

I have refrained from water change/dosing until I get some advice here. What would you advise as the best course of action?

I think seeing as you’re already started adding corals .
focus more on stability rather than ups and downs adjusting and c numbers.
From one test to another there are huge fluctuations
Mag -1380 to 1500
Cal 405-440
Alk 9.2-8.4
And salinity from 1.028 -1.025

not 100% sure if both tests are accurate or correct . Or which one is .

 

[WTJReef]

Alright Guys,

The system is 320L including the sump. I performed a 50L water change today using store bought "Natural Sea Water" and upon retesting my magnesium was even higher

New numbers:

Mag 1600+ (Tested twice with high level of care)
Cal 440
Alk 8.4
Salinity 1.027 ( I recalibrated my Refractometer today so I am confident in this reading)

What is the story with my magnesium? I did not expect it to go up after the water change. Now I suspect this is what happened the first time as the jump from 1380 to 1500 happened right after a water change.

Are these levels going to harm my fish/coral? How do I go about lowering Mag? Seeing as my salinity is still a little above 1.025, could I add RO water and would this assist in lowering the Mag?

Corals still looking fine and were glued into their positions today.

I will be making my own salt in future, my RO system is just on back order.

 

[LeftyReefer]

Alright Guys,

The system is 320L including the sump. I performed a 50L water change today using store bought "Natural Sea Water" and upon retesting my magnesium was even higher

New numbers:

Mag 1600+ (Tested twice with high level of care)
Cal 440
Alk 8.4
Salinity 1.027 ( I recalibrated my Refractometer today so I am confident in this reading)

What is the story with my magnesium? I did not expect it to go up after the water change. Now I suspect this is what happened the first time as the jump from 1380 to 1500 happened right after a water change.

Are these levels going to harm my fish/coral? How do I go about lowering Mag? Seeing as my salinity is still a little above 1.025, could I add RO water and would this assist in lowering the Mag?

Corals still looking fine and were glued into their positions today.

I will be making my own salt in future, my RO system is just on back order.

If your salinity was 1.025 at the time of the first test, and 1.027 at the time of the second test, then magnesium being higher during the second test would also be expected.

To reduce the salinity, you need to remove saltwater and replace it with a like amount of RO. Do you have an ATO?

 

[WTJReef]

If your salinity was 1.025 at the time of the first test, and 1.027 at the time of the second test, then magnesium being higher during the second test would also be expected.

To reduce the salinity, you need to remove saltwater and replace it with a like amount of RO. Do you have an ATO?

Yes I do Have an ATO

 

[LeftyReefer]

Yes I do Have an ATO

OK good.

I'd just replace some tank water with some RO, getting your salinity down to where you want it. Then let the ATO keep it steady. I don't think any of the numbers you've posted so far are out of line... all are fine/safe for fish and corals. Keeping them steady is the key.

 

[Aqua Man]

Salinity is parts per trillion. Mag is parts per million. Would Mag really go up that much with that small of a salinity change?? Very curious!!

 

[Aqua Man]

If your salinity was 1.025 at the time of the first test, and 1.027 at the time of the second test, then magnesium being higher during the second test would also be expected

Salinity is parts per trillion. Mag is parts per million. Would Mag really go up that much with that small of a salinity change?? Very curious!!

@Randy Holmes-Farley asking for clarification on theses statements above.
Thank you !!

 

[LeftyReefer]

Salinity is parts per trillion. Mag is parts per million. Would Mag really go up that much with that small of a salinity change?? Very curious!!

Who is to say if his Mag really went up that much?? I see too many variables in the testing to draw too many conclusions about what the levels actually were at any one time.

better baseline testing needs to be done from here on out to learn anything.

 

[Aqua Man]

Who is to say if his Mag really went up that much?? I see too many variables in the testing to draw too many conclusions about what the levels actually were at any one time.

Agree, it’s just a general question on my part. Just curious if it’s linear movement. Took me awhile to wrap my head around the calcium and alkalinity uptake being linear. Of course the caveat being the testing done are correct and accurate.

 

[Randy Holmes-Farley]

A specific gravity change from 1.025 to 1.027 will raise magnesium and everything else by a factor of 27/25, or 1.08.

Thus, magnesium at 1380 ppm becomes 1380 x 1.08 = 1490 ppm.

 

[WTJReef]

Hi All,

Ill go ahead and put an end to the speculation - Ive made what I feel like is an obvious and stupid beginner error that gave rise to those Magnesium readings.

While I was rinsing the testing vials with water from my DT multiple times between tests last night, while I was testing I noticed a thin white film on the inside of the magnesium vial. I then re read the testing manual and realised an RO rinse and wipe out was necessary and that this film can lead to erroneously high results.

The correct Magnesium reading was a much more respectable1400PPM

I rinsed all the vials and retested. Calcium and kH levels were constant at 8.4dKH and 440ppm and I have maintained these levels since I performed my first calcium dose after my initial visit to the LFS. Prior to dosing, my levels were consistent with the readings with the LFS readings, however I did not have a refractometer at this point.

Salinity was correct, however since performing a gradual RO switch out as suggested I have lowered my salinity to 1.026 from 1.027

Apart from the obvious mistake I did make, I'm interested to see how my baseline testing could be improved. I have been testing at the same time every evening this week. I dose where necessary immediately after testing so the levels have a full 24 hours to rebalance before I touch the tank again. As far as I was aware the Red Sea titration tests were a reputable product

 

[Randy Holmes-Farley]

Apart from the obvious mistake I did make, I'm interested to see how my baseline testing could be improved. I have been testing at the same time every evening this week. I dose where necessary immediately after testing so the levels have a full 24 hours to rebalance before I touch the tank again. As far as I was aware the Red Sea titration tests were a reputable product

I'd suggest there's no need to test magnesium more than once every 2-4 weeks, and longer once you set up a good baseline understanding.

It never depletes more than about 1/10th of the calcium depletion rate nor more than 1-2 ppm per day, and often the decline is totally lost in water changes, salinity variations, and test kit precision/accuracy.

 

[Moonwrassler]

This dialogue has been very educational, thank you.
Question: I too have had a surprise swing up in Mg in the past week (probably dosing related + salinity climb from 1.025 to 1.026). My question is whether there's any danger of harm to corals or fish from a Mg level at 1620.

Context: Tank has been up for 3 months and just got out of Ugly algae phase--all the GHA and various slime mats (that I'd been leaving alone to outcompete a mild dinos outbreak) just melted away in the past 10 days; couldn't believe it. Should I be concerned that this isn't a coincidence but is actually a water chemistry problem?
With the exception of Mg parameters below have been pretty stable:
pH 8.2
KH 9.8
Salinity 1.025-1.026
CA 440 (had climbed to 500 while dosing but have gotten it back under control
Mg 1620 (had been 1380-1440)
Nitrate 10 - 20
PO4 0.3 - 0.5 (was dosing to beat back dinos)
Ammonia 0
Nitrite < 0.05