Dosing magnesium? Calcium?


Reefing newb
Hey all. So my suspicions first arose when I noticed a whole lot of pink coralline showing up. Which was great. The contrast between the two, purple and pink looked quite amazing. However, three days later the pink had turned all white. I suspected lack of calcium since I have added a lot of sps lately. I then proceeded to check my calcium which was 380 quite low for my tank. I tested this 2 days before my weekly water change was due. Normally a constant 450 with reef crystals. I then purchased alkalinity and magnesium tests since I know these 3 go hand in hand. 24hr s after a water change I proceeded to test for the3 parameters mentioned above. On March 30th they were as follows :
Calcium 420
Alkalinity 9
Magnesium 1440
All great from what I've read. Right where I want them to be. Then on April 2nd (today) I tested again the results were as follows:
Calcium 400
Alkalinity 8.9
Magnesium 1350
All still within range from what I've read. I keep my salinity at a constant 1.026. I've never had to dose anything ever before. I plan on doing another set of tests on Friday. My question is from the data you see will I need to dose magnesium if it keeps declining as it is? And will that keep the other two in check? I apologize if this isn't enough data yet maybe to make an assumption but this is all new to me. Also I have no sump or dosing pumps so any product that anyone has used by adding directly to the DT with great results would be greatly appreciated. Any info at all really would be much appreciated. I'd like to here from some trusted fellow reefers rather than random info on the Internet. I want to nip this issue in the but as soon as possible so I plan on going out this weekend if needed to get some dosing supplements. Also if it helps, I read reef crystals when mixed should have a calcium reading of 500 after I mixed a batch it read 420. Bad batch of salt perhaps? All just speculation. Again any advice would be great. Sorry for the rambling. Been a longggg day. :confused:
I would question the accuracy of your mag test results. Mag test kits can be hard to read. When calcification occurs (corals forming their hard skeletons and coralline algae growing) a set ratio of calcium, alk and mag is used. For approximately 18ppm of calcium used, 1meq/l (2.8 dKH) of alk is used and 2ppm of mag is used. So taking that into consideration, the drop you see in mag is way off. I would run a few more tests and see what kind of results you get.

On a side note, I'm not a fan of Reef Crystals, even though many people do like it. The reasons being it contains vitamins, but no one knows what they are, if they are needed and what they break down into. The parameters are also very much different (higher) than the average parameters of seawater out on the reefs. On average, Reef Crystals gives you around 490 calcium, 13 dKH alkalinity and 1440 mag. Natural seawater is around 420 calcium, 7 dKH alkalinity and 1280 mag. I use Instant Ocean, which mixes to around 400 calcium, 11 dKH alkalinity and 1350 mag.
Thanks ccapt. That does make a lot of sense and I have heard before of the ratios used of the three. I did have some difficulty with salifert mag test. It's a lot different then the api test kit I'm used too. I'll do some more tests tonight. Also I always have an air bubble between the plunger and the liquid. In the instructions it says this will not effect the results. Which is dandy but do I take the final number from the plunger line or the liquid line? When I initially pull liquid into the plunger I pull until the liquid is at the required mark not the plunger line. Thanks for the input it's somewhat still confusing for me. So is that what you aim for ccapt? The initial readings when you mix of 400 11 and 1350?or do u dose to get higher levels?
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Thanks Emmett, I reread the instructions and seen that part. Lol. OK, so I just took three more magnesium tests with all different results. First was 1380 second was 1250 and third was 1270. So I'm guessing by these results my mag is probably In the high 1200s maybe creeping into the very early 1300s. Would I be correct at assuming so?
i would say close and on the 2 ml syringe make sure you have a bubble in it too. this test kit can be tricky to use but once you get the hang of it i think it does a good job. one more tip is you are puttin in the last solution make sure you go one drip at a time
One drip then shake.. Rinse and repeat? Takes forever I was doing around 3 drips then shake until I got somewhat close to where it would be roughly then one at a time. Is that OK? Or should it always be one at a time. Not once did I drip 3 times shake and found it had turned colour it was always on the one drip cycle. Just so you know I didn't accidently over drip.
Cool thanks everyone. I'll do a few more tomorrow. See how it works out I'll keep this thread updated In hopes of more good advice. I'm really hoping I don't need to start dosing.
I'm also trying to decide if I need to dose. I was using instant ocean salt switch to kent and now mAybe I will try reef cristals.

I have run a series of test with the red sea kit but now I can't remember if I read from the plunger or liquid on all the test. I'm on my 3rd week of test, one before water change and one after but now I think I will start over.
I'm also trying to decide if I need to dose. I was using instant ocean salt switch to kent and now mAybe I will try reef cristals.

I have run a series of test with the red sea kit but now I can't remember if I read from the plunger or liquid on all the test. I'm on my 3rd week of test, one before water change and one after but now I think I will start over.
Plunger line
OK.... I now am confident that I have the salifert testing kits mastered. I'm getting multiple readings exactly the same. Now, my question is, has anyone ever had salt go bad? Not necessarily go bad but is it possible after time for it to lose its trace elements as time goes on? The reason for my inquiry is that I tested my tank before my weekly water change and my readings were
Alkalinity :7.3
Magnesium :1260
Calcium :400
then around 6 hrs after my water change my readings were as follows
Alkalinity :7.5
Magnesium :1270
Calcium :380
Salinity in my tank was consistent both tests the only difference was temperature roughly. 5 of a degree difference. Am I wrong or should I see more of an increase in these numbers. Did I test too soon after my water change maybe? I only do roughly 11. 25% water change around 2.25 gallons. I buy a 50 gallon bag of reef crystals so as you can imagine it takes me quite a long time to go through it. Maybe 6 months. I do however twist the bag shut and wrap a hair elastic around it multiple times to seal it. I'm thinking if it's possible that over time it's lost some of its coral goodness. Has anyone ever heard of this? Any ideas or suggestions would be great! Also each test was conducted multiple times before and after my water change with the same results. :thumbsdown:
Did you test the new water before adding it? Don't go crazy chasing numbers. Your parameters look good. Calcium may be a little low but not low enough to really worry about. I would sort of think there may be a testing error on that final number.
As far as wondering if they should be higher after a water change, to make the math easier, let's say you do a 10% water change.
If your alk was 7.3 and you did a 10% change and the new water was 11, your new alk would be 7.67.
If your mag was 1260 and the new water was 1440, your new reading would be 1278.
If your calcium was 400 and the new water 490, your new reading would be 409. For the calcium to drop from 400 to 380, the new mix would have to be 200.
There have been cases of bad batches of Reef Crystals in the past. You can Google it.
Thanks cccapt. Much appreciated,.I did google the bad batches. Just a lot about people using it and nuking their whole tank. Thank god that's not my case.