Low Mag kill coral?

S

steallife904

New member
May have discovered an issue I have been having last night with some of my corals (mainly my LPS) receding and dying off. My Mag level was 840... have no idea how long its been low, since my calc and alk where in range never though to check it (calc 450, alk 7.8). Would low mag kill the corals? if so which I believe the answer is yes that more than likely is my issue.
 
curious how you are keeping Ca up with Mg that low. Usually Mg helps keep Ca in solution and once it gets below about 1000 makes it very hard to maintain Ca over 400-410. Whats your gravity?
 
found another issue, seems my salinity was 1.028 in the tank. will slowly bring it back down to 1.025. I was dosing calc and alk daily. I have stopped while I am balancing everything out. no idea how long the mag was this low so do not know how the calc was keeping up????
 
the Ca is up because your salinity was up. The test is calibrated for a lower gravity like 1.023-1,025. So your Ca is probably below or right at 400 when you adjust gravity and your Mg is even lower. The high overall gravity could be causing the problems. You should do a substantial water change probably also are you using a refractometer to measure salinity?
 
yes using a refractometer. I have calibration fluid as well to make sure its calibrated. I started taking out some of the tank water and replace with RO/DI. I brought it down to 1.027 last night. Will do a little more today, trying not to do it all at once to shock the system. Also dosing Mag to bring it up.
 
ok I will run a sample in this weekend. I though the same thing. I have tested it 6 times now and always get around 840. Im using a red sea mag test kit.

Salinity is now 1.026. I think I am going to get it closer to 1.025. I think what I may have put in more new salt water during water changes than I was taking out a few times.... common sense should have told me if I am putting saltwater in but not taking out the same amount of saltwater... it will get salter. not sure why I even did that since I have never added and removed different amounts in the past.
 
Yes, always use fresh water (ro/di) for replacing water lost to evaporation. The water evaporates but the salt does not.

Yes, in my experience super low mag like that can take out LPS pretty quickly.

Either purchase or make some magnesium supplement solution and add it.

I dose mag via pumps and timers just like my alk and calcium. I make up a solution from magnesium sulfate and magnesium chloride which I get from BRS. Very economical.
 
i have an auto top off that replaces evaporated water with fresh ro/di. i believe during the last few water changes though i put in more than i took out of saltwater which slowly brought up the salinity. I have been trying to bring it down by scooping out a cup of salt and add a cup of fresh once or twice a day but it doesn't seem to want to come back down very fast.
I do have a doser that doses calc and alk but not mag... yet. I will need to add a container to it to start dosing mag but for now i have been dosing it myself everyday since i found it to be low. I actually have the dosers off rigt now while i am trying to get my water back in line. Just a slow process.
 
I have not had a chance yet to take a water sample to the LFS but have been dosing mag everyday close to 2 weeks... I checked mag level last night and it has barely moved. It was around 880. I know its hard to bring mag up but dang. I already ordered more mag mix from BRS and a dosing container to add mag to my doser going forward. Is my tank just drinking mag like crazy? I need to check the mag of my salt on the next water change, I use Kent reef salt if that helps but maybe the mag in it is low. Should I mix up a large dose of mag and put in tank or keep going with small amounts???
Right now I am using seachems Reef Advantage Magnesium, dissolving about 7tsp in a cup of water. Have been dosing that every day.
 
BRS has a magnesium calculator on their website you may want to visit to get an idea of how much to dose. In general, I add way less mag than alk or ca, but I'm maintaining my level versus trying to raise it significantly. It sounds as though your 7 teaspoons (35ml, a bit more than one ounce) is not sufficient.

While making adjustments to alkalinity has to be done slowly and carefully, one can be more abrupt with mag. IMHO you could easily take it up 200-300 points per day without shocking your tank.
 
guess that's what I will do then, up the dosage to try and make an impact.
I did use there calculator and it appears I will need a ton to bring it up... want to say it was like 6000ml (I got brs mix solution)
 
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