100 ppm drop in Magnesium.

[Gellisjr1]

Hello everyone.

I am a newer member to this forum. I have a 35 gallon cube reef tank. The tank is about 7 maybe 8 months old. Short back story I purchased my first corals several months ago. One of those corals was a nice little Torch. The Torch started to show signs of distress 2 weeks after putting it in my tank. By the time I found out the magnesium level in my tank dropped to 1150 ppm, it was too late for the coral. It died. I contribute this due to my misunderstanding of how to dose the product All for Reef by Tropic Marin. I was educating myself about what dosing is and trying to figure out what and how much product to dose. Then I came across this product that seemed like the perfect answer to my dosing needs. Does this product in my tank and track Alkalinity and I would be golden, So I thought. I found out where I made my mistake. That was not having the necessary test kits for the foundation elements, to get the parameters in check before starting dosing the product All for Reef. It was a hard lesson to learn.

I have since reset parameters and started over dosing the All for Reef to my tank again. I have been diligent in testing of my water parameters. I have been testing and dosing the tank the best I can with manual dosing. At least until I can get my dosing pumps and reservoir system set up. I am almost there. From watching my parameters closely Calcium is consistently 450 - 470 ppm (Salifert Test kit), Alkalinity has stabilized at 9.5 - 9.7 dkH (Hanna Checker), Temp 78 degrees F with a +/- of 1 degree F. (infrared digital temp scanner)Salinity is consistently 1.025 due to my ATO. (Refractometer) pH 7.8 - 8.0 (API color match kit, too much room for error. Considering the Hanna checker or Monitor with probe I need numbers for this.) Magnesium on the other hand has had sudden big drops in ppm. This last time on Monday night i did my nightly water tests Magnesium was at 1425 ppm (Aqua Forest test kit). The very next morning I noticed one of my Hammer corals looked a little stressed & shriveled up. I checked my Magnesium parameter. Then a second time to confirm the first reading. My magnesium dropped a little over 100 ppm over night. All my daily tests up until this point were consistently mid 1400 ppm readings for magnesium. I am having a very difficult time trying to figure out how much Magnesium to dose daily when the parameter stays so consistent with the All For Reef then bam the floor drops out on the magnesium. I brought the magnesium level back up slowly to the mid 1400's and confirmed this yesterday after several hours after my final dose of magnesium. I don't understand why this is happening.

From analyzing my water parameter readings it looks like the only elements that I will need to dose daily is going to be the All for Reef and Magnesium. At least for the time being until my corals start to grow and use up some of the other elements. Then make minor adjustments with the All for Reef to stabilize Calcium & Alkalinity. I would appreciate some insight why this is happening? Coral growth? Addition of new corals weekly? Coralline algae taking off? How do I hone in on a daily dosage for Magnesium beside trial and error.

 

[blaxsun]

I'm inclined to lean towards testing error (100ppm drops in magnesium don't typically happen - even with larger water changes).

 

[Troylee]

I’d say testing error..

 

[Gellisjr1]

Definitely not testing error. Double checked the readings with a second test then added 40mL magnesium and test to track the ppm readings to make sure how much the adjustments were moving the numbers. It took a total amount of 120mL of Magnesium to bring readingsback to 1435 ppm. Confirmed yesterday. This is not the first time its happened. All my Magnesium tests have been consistent. I have a record of all my tests. I have a log book and write everything down and what adjustments I made or didn't make.

 

[Troylee]

100% is… @Randy Holmes-Farley will chime in.. it’s impossible for it drop 10ppm per day without your calcium dropping to unsafe levels.. 100ppm is outta this world lol.

 

[Randy Holmes-Farley]

Definitely not testing error. Double checked the readings with a second test then added 40mL magnesium and test to track the ppm readings to make sure how much the adjustments were moving the numbers. It took a total amount of 120mL of Magnesium to bring readingsback to 1435 ppm. Confirmed yesterday. This is not the first time its happened. All my Magnesium tests have been consistent. I have a record of all my tests. I have a log book and write everything down and what adjustments I made or didn't make.

Kits often do not give accurate results, even when you used them perfectly.

Magnesium CANNOT drop 100 ppm by consumption unless calcium dropped over a thousand ppm.

Either the salinity dropped significantly, one or both of the test results are in error, or you added over a thousand ppm of calcium in that time period where magnesium was dropping.

 

[Gellisjr1]

I really am trying to be open minded and not be ignorant to your answer. I want to understand what is happening here. I just cannot ignore how the testing results followed the corrective measures. Then to have an absolute positive improvement in the condition of my reef inhabitants. What should I be using for testing?

 

[Randy Holmes-Farley]

I really am trying to be open minded and not be ignorant to your answer. I want to understand what is happening here. I just cannot ignore how the testing results followed the corrective measures. Then to have an absolute positive improvement in the condition of my reef inhabitants. What should I be using for testing?

I've come to the conclusion that magnesium should NOT be tested, except in a very well established reef tank that is getting lots of alk and calcium with an additive that does not contain desirable levels of magnesium. It causes more angst than it is worth. it does not ever move around large amounts on its own.

I can easily explain what happened with your dosing, by any of the three mechanisms I suggested above.

Assume magnesium is low because salinity is low. Adding more magnesium makes it rise by the expected amount. What is your salinity and how are you measuring it?

Assume magnesium is false low due to test error. Suppose it reads only 90% of the expected value. Then a normal 35 ppt salinity magnesium level of 1285 ppm becomes 1157 ppm. Then you add 100 ppm magnesium, and the test kit value rises by the kit factor of 90 ppm, and gets to where you think it should be. Still the kit was the issue.

Or, everything is as expected and you have added 1000 ppm of calcium since the last magnesium measurement. How much and how are you adding calcium and alkalinity?

There is really NO other way for magnesium to drop 100 ppm, aside from water changes with a low magnesium mix. Are you doing water changes and have you measured magnesium in your mix?

 

[Gellisjr1]

I test salinity with a refractometer calibrated using RO water to read zero on the scale. My Salinity is 1.025 -1.026 depending on if the ATO failed to come on. I test parameters everyday in the evening when I get home from work. I use Instant Ocean Reef Crystals premixed to 1.025sg, 5 gallons at a time using RO/DI water heated and mixed with a powerhead in the bucket. I change this amount every week on Tuesdays on my day off from work.

I have been dosing Tropic Marin's All For Reef. It is supposed to be an all in one supplement. That maintains Calcium, Alkalinity, Magnesium & trace elements in one solution. I am currently dosing 7.5mL of All for Reef daily. My calcium tests only fluctuate very little 450 ppm - 470 ppm. According to the directions on the bottle for All for Reef they claim I only need to monitor the Alkalinity level to maintain system parameters. In my case Magnesium is the only element that I am having an issue with, while using All For Reef. In your opinion should I discontinue the use of All for Reef and just dose Calcium, Alkalinity & magnesium separately as needed? I was originally going to do it this way following Red Sea's Recipe for a mixed reef aquarium on there web sight. It gives daily dosage recommendations of each element. The reason i changed my mind not to follow the Red Sea recipe is because of the amount of dosing pumps I would need to dose all 7 of the elements they recommend (Calcium, Alkalinity, Magnesium and 4 trace elements)

 

[Randy Holmes-Farley]

The difference in magnesium between sg = 1.025 and sg = 1.026 is about 50 ppm, so salinity variability may be a large part of the explanation, especially since the salinity measurement has substantial natural variability when measured this way.

Which refractometer? Some cannot correctly be calibrated with ro/di despite manufacturer claims they can.

 

[Randy Holmes-Farley]

I’d keep using the AFR, and not focus on frequent magnesium testing. It cannot ever change rapidly except by salinity.

 

[Troylee]

All for reef is fine and yes just watch your alk.. mag isn’t that important like Randy mentioned and doesn’t drop fast at all! In fact if you’re testing that regularly you’ll see your mag go up as your calcium drops it’s a trend that a trident always shows… I can’t say how accurate the trident is or any test kit we use honestly but they’re all good base lines.. I have a trident but check it with my salifert test regularly to make sure it’s not wondering away.. I use all for reef and top off with kalk since my tank is so large and getting full of corals the demand is getting higher.. all for reef works well and does what it claims.

 

[Gellisjr1]

This is the Refractometer I purchased on Amazon. Amazon product

 

[Gellisjr1]

If it would help. I can scan my log recordings and you can review them and make recommendations. I just would need some time to gather them up and bring them to work to scan them.

 

[Troylee]

If it would help. I can scan my log recordings and you can review them and make recommendations. I just would need some time to gather them up and bring them to work to scan them.

To be completely honest with you I think you’re over doing the testing… a tank of your age should be pretty much on auto pilot by now. You could test once a week and be fine with the routine you’re doing of water changes etc.. the only thing I can say to keep testing if anything every few days would be your alk till you got your all for reef dose dialed in! Once that’s dialed, I wouldn’t bother testing unless something seems off… you should have a good eye for your tank now and know when somethings off and how the corals react.. don’t chase numbers or your tank will never settle and it won’t be happy and you won’t be happy! It’s a viscous circle haha!

 

[Randy Holmes-Farley]

This is the Refractometer I purchased on Amazon. Amazon product

I believe that is not a true seawater refractometer, but is, as is often the case, a brine refractometer being sold to marine hobbyists without knowing that it is inherently inaccurate when calibrated at 0 ppt.

My suggestion is to buy or make a good 35 ppt standard and use that for calibration.

 

[Gellisjr1]

I may have found the reason why my magnesium level dropped off so abruptly. It appears that my Coralline algae is really starting to take off. It is starting to grow on my back glass and I can see it encrusting on some of the rock & frag plugs. I just realized this with in the past couple days. I was cleaning my glass with my magnetic scrubber and had a couple stubborn spots that didn't want to come off. This is when I started to examine the spots and started looking more intensely for Coralline growth and sure enough it is all over my rock work. It's a little hard to pick out on the rocks because my rock is the purple man made Caribsea rocks.

 

[Randy Holmes-Farley]

I may have found the reason why my magnesium level dropped off so abruptly. It appears that my Coralline algae is really starting to take off. It is starting to grow on my back glass and I can see it encrusting on some of the rock & frag plugs. I just realized this with in the past couple days. I was cleaning my glass with my magnetic scrubber and had a couple stubborn spots that didn't want to come off. This is when I started to examine the spots and started looking more intensely for Coralline growth and sure enough it is all over my rock work. It's a little hard to pick out on the rocks because my rock is the purple man made Caribsea rocks.

Just remember that while coralline is a large user of magnesium, it still needs to consume about 18 ppm of calcium and 2.8 dKH of alk for each 2 ppm of magnesium consumed. Real magnesium consumption is never more than about 2 ppm per day.