Effects of low magnesium?

[Nick Steele]

Okay so over the past month I’ve noticed my magnesium has slowly started to deplete from what I believe to be coralline growth. I was curious as to if this could be why some of my corals don’t look too happy?

Pink hammer been in system for 2 months did well first 6 weeks or so but is now not as open as before.
Before

Today

Superman digi is two weeks old and it started off well today I noticed white skeleton near the bottom of the frag and a bare spot on the backside of frag.

Two weeks ago

Today
Can see the skeleton on the bottom and stretching up the right branch.

Here you can see the bare spot without any polyps

Everything in tank has been stable besides magnesium (working on fixing it)

Parameters
Alk 10.9
Calc 470
Mag 1100
Ph 8.1
Temp 78
Nitrate 5
Phosphate 0-.03 with salifert (very slight blue)

Running one AI 16hd for light.
Only run filter floss and some rock rubble nothing else for filtration.

Can this all stem from low mag levels or something else?


Here’s a full tank shot just in case you can see anything else.

 

[Greg P]

Looks like possibly a lack of light issue.
What fixture and schedule are you running?

 

[Nick Steele]

Looks like possibly a lack of light issue.
What fixture and schedule are you running?

It’s an AI 16hd and this is the schedule I’m running Same schedule since the beginning too

 

[Greg P]

I'm a T5 guy
Hopefully some LED peeps will get involved

 

[Greg P]

As to your original post, I personally don't see your Mag level causing your issues, based on your other tests.
If your Mag were low enough to cause you difficulty getting your Alk and Ca inline, then there'd be reason to raise it.

Not saying your lighting is the issue but, based on your pictures, I'd say they are starving for light. The 'patches' on your Digi are in what I see as 'shaded' areas.
But don't ramp up your lighting until you hear from someone familiar with your fixture.

Consider starting a post in the lighting section with your above photos and concerns.

 

[Nick Steele]

As to your original post, I personally don't see your Mag level causing your issues, based on your other tests.
If your Mag were low enough to cause you difficulty getting your Alk and Ca inline, then there'd be reason to raise it.

Not saying your lighting is the issue but, based on your pictures, I'd say they are starving for light. The 'patches' on your Digi are in what I see as 'shaded' areas.
But don't ramp up your lighting until you hear from someone familiar with your fixture.

Consider starting a post in the lighting section with your above photos and concerns.

That’s exactly what I did posted in the light forum. Only change would be almost 3x my uv and violet channel so idk maybe I’ll do it.

 

[Greg P]

Since I'm unfamiliar with LEDs, your chart means pretty much nothing to me.

How many hours @ how many percent does it equate to?

With T5s, I prefer an average of about 3-4 hours @ 100% and a total run time of 10 hours.
I start with a pair of bulbs, adding a pair each hour until all 8 are on.
3 hours later I start turning them off in pairs.

So I ramp my system from 25% to 100% over 3 hours, run for 3 @ 100%, then back to 25% over 2 hours.
Then an hour @ 25% before shut-down.

Because you have so much more control than I, your programming is vastly different than mine.

Link your other post for me and I'll follow along to learn.

 

[Greg P]

Had a look at your other thread.
I'd be curious to see what opinions you'd get with a different thread;

Is this lighting schedule enough for my corals? I'm having the following issues ....

 

[Randy Holmes-Farley Verified Community Expert]

Magnesium testing issues are common, Have your tried that kit on some new salt water?

That said, if magnesium is really all the way down to 1100 ppm and the salinity is for sure not too low, there's no reason to not raise it.

 

[Nick Steele]

Magnesium testing issues are common, Have your tried that kit on some new salt water?

That said, if magnesium is really all the way down to 1100 ppm and the salinity is for sure not too low, there's no reason to not raise it.

I’m positive the mag test is being done correctly. NSW mixes at 1250ish and tank will go up when I do water changes. But has been slowly dropping with the coralline buildup I believe.

Is it usual for the mag level to drop without alk or calc because of coralline buildup? I will take a water sample to my lfs on Wednesday and pick up a mag supplement as well to see if it helps.

 

[Randy Holmes-Farley Verified Community Expert]

I’m positive the mag test is being done correctly. NSW mixes at 1250ish and tank will go up when I do water changes. But has been slowly dropping with the coralline buildup I believe.

Is it usual for the mag level to drop without alk or calc because of coralline buildup? I will take a water sample to my lfs on Wednesday and pick up a mag supplement as well to see if it helps.

It cannot drop on its own. Coralline uses a lot of magnesium, relative to other organisms, but still less than it uses calcium by several fold.

 

[Randy Holmes-Farley Verified Community Expert]

Aquarium Chemistry: Magnesium In Reef Aquaria

This article details the nature of magnesium in seawater, how it is added, measured, and removed from marine aquaria, and how it impacts the maintenance of calcium and alkalinity.

reefs.com

Interestingly, coralline algae that normally packs a large amount of magnesium into their calcium carbonate deposits (>4 mole percent magnesium carbonate, or >1% magnesium by weight) has been shown to incorporate less magnesium when the magnesium content of the water is reduced. The amount incorporated is directly proportional to the magnesium concentration. Consequently, the amount of magnesium that they consume in aquaria is dependent on the magnesium content of the water. This effect is also likely to extend to other calcifying organisms as well.

Bear in mind a coral that has 4.4% magnesium by weight in its skeleton must have something like 30+% calcium, and the rest carbonate, so it is using a lot of calcium and alk as well.

 

[Nick Steele]

Interesting maybe I am messing up the test then I’ll see what my lfs says on the testing. I’ll go through and read that link. Thanks!

 

[Randy Holmes-Farley Verified Community Expert]

Interesting maybe I am messing up the test then I’ll see what my lfs says on the testing. I’ll go through and read that link. Thanks!

It might be low if salinity is low, or if it declined over a long time, or you had a bad batch of salt in the past.

 

[Nick Steele]

It might be low if salinity is low, or if it declined over a long time, or you had a bad batch of salt in the past.

Salinity is 1.025-1.027 used 1 refractometer a Hannah salinity pen and apex probe last week on my tank and friends tank who has an apex. I run 1.026 he runs 1.025. All devices were within .001 of each other. It’s only a 20G tank and I’m still on my first bag of salt maybe halfway done with it. Always mixes at 1250 mag at 1.026 salinity. Mags declined from 1250 in beginning to 1100 now about 5 months from start up.

 

[Randy Holmes-Farley Verified Community Expert]

Salinity is 1.025-1.027 used 1 refractometer a Hannah salinity pen and apex probe last week on my tank and friends tank who has an apex. I run 1.026 he runs 1.025. All devices were within .001 of each other. It’s only a 20G tank and I’m still on my first bag of salt maybe halfway done with it. Always mixes at 1250 mag at 1.026 salinity. Mags declined from 1250 in beginning to 1100 now about 5 months from start up.

That is reasonable if you are dosing 1 dKH per day, and supplementing with calcium chloride and sodium carbonate.

i show here that dosing 1.1 dKh per day and correcting for salinity rises (by far the biggest effect on magnesium, not actual consumption) magnesium will decline from 1290 to 880 ppm in a year.

http://reefkeeping.com/issues/2006-02/rhf/index.php

 

[Nick Steele]

That is reasonable if you are dosing 1 dKH per day, and supplementing with calcium chloride and sodium carbonate.

i show here that dosing 1.1 dKh per day and correcting for salinity rises (by far the biggest effect on magnesium, not actual consumption) magnesium will decline from 1290 to 880 ppm in a year.

http://reefkeeping.com/issues/2006-02/rhf/index.php

That’s the thing not dosing yet haven’t seen a need to as no other parameters are dropping. I will supplement mag here soon and maybe that will help out with growth. Only 13 frags now 4 zoas, 3 different montis, Xenia, gsp, rainbow acan, pink hammer and a purple tip frogspawn. Everything looks nice besides cyphastrea, the monti in question and pink hammer. Hammer and frogspawn seem to be splitting though but I’m guessing water changes are keeping up on this front.

 

[Randy Holmes-Farley Verified Community Expert]

That’s the thing not dosing yet haven’t seen a need to as no other parameters are dropping. I will supplement mag here soon and maybe that will help out with growth. Only 13 frags now 4 zoas, 3 different montis, Xenia, gsp, rainbow acan, pink hammer and a purple tip frogspawn. Everything looks nice besides cyphastrea, the monti in question and pink hammer. Hammer and frogspawn seem to be splitting though but I’m guessing water changes are keeping up on this front.

If you are not dosing, the magnesium essentially duplicates what came in the salt mix. There is no other alternative. Perhaps your salinity is creeping down.