Magnesium observations

[zygote2k]

I work on a tank that has a constant bryopsis problem and it's only kept in check by high levels of magnesium.

I would pull it out by hand for months and then a while back, I started using Kent Tech M like everyone else suggested but it got to be too expensive.

I went to the Randy Holmes Farley method and bought Mg Chloride and Mg Sulfate and mixed it myself. This way was far cheaper but the cheap versions of these chemicals were very dirty and when mixed, had to be strained for contaminants. 

I also noticed an increased frequency of lineset failures on the dosing pump from using the RHF 2 part. This alone made me switch to BRS chemicals as they mix clean and clear.

I learned that flushing dosing lines weekly helps prolong their longevity.

So after dosing 4 gallons of RHF Mg over the course of 6 months, the Mg levels were at 2250 and all of the bryopsis and HA died away completely. The snails and starfish also bit the dust so I dropped it back to 1800 ish and everything did fine for about 6 months. 

I got lazy. I stopped dosing Mg because I didn't see a need because there was no Bryopsis.

A year goes by and I forget all about Mg. I did notice a decline in the dominant SPS species in the tank followed by an explosion of GSP, Blue Cloves, and Anthelia.

I have now been battling the Anthelia and since it grows so quickly, it creates pockets of stagnant water which spawn Derbesia, HA, and the dreaded Bryopsis.

The Mg tests at 1180 and I proceed to dose BRS Mg by hand.

I raised it to 2250 as of Friday over the course of 2 months and the snails and starfish seem to be unaffected. I'm going to stop dosing and let it drop to about 1700 and see if I can maintain it there.

Some of the noticeable effects of high Mg are  the browning of Purple Nurple, Pokerstar Monti, Purple Porites, Orange Cap, Setosa, Pink Birdsnest. The reddish corals seem to be most affected but all of the green ones are doing fine and seem to be completely unaffected.

Acans are fluffy, Anthelia is booming, Green Pocillopora still bright green.

 

Does anyone know how Mg affects pigmentation of corals?

 

[sachabballi reef]

I assume high levels kill all pods as well?

 

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[zygote2k]

I haven't seen any pod deaths.

[sachabballi reef]

Excellent thanks !

 

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[Origami]

Good observations, Rob. So, even after an extended time with elevated magnesium, you're saying that the bryopsis was not completely eradicated, but only knocked back? (It did come back so it was still in the tank it seems.)

 

I believe that most saltwater organisms are quite tolerant of elevated magnesium. However, magnesium is a major ion in salt water. Here's a great graphic that I came across a few days ago and which gives an overview of the composition of sea water:

 

 

It basically shows that about 3.7% of sea water's salinity comes from magnesium. When you added the magnesium chloride and sulfate, you also added close to twice the equivalent ions in chloride (I say close, because of the ratio of sulfate to chloride that you use in RHF's standard mix). So, when you nearly doubled the concentration of magnesium, I would expect close to a 9% upward shift in salinity - assuming all other things remained equal. This may have factored into some of the deaths of snails and stars as they are very sensitive to salinity changes if too rapid. If you pulled the salinity back down with fresh water, then the other ions are diluted, too, including calcium and alkalinity (which you would then probably compensate for) and all the other trace ions. Some of those may play into coloration - not sure about that, though.

[AlanM]

Would the increase in salinity due to the magnesium chloride be measureable with a refractometer?  If so, and you were running 35ppt before adding it, 9% increase is 38.5ppt, so it would be seeable on a refractometer for sure if the magnesium affects the reading through the prism in the same way that NaCl does.

[paul b]

I haven't seen any pod deaths.

I looked very closely and this pod --------> . <---------- seems to have died. I will do a autopsy to see if it had anything to do with magnesium.

[Origami]

Would the increase in salinity due to the magnesium chloride be measureable with a refractometer?  If so, and you were running 35ppt before adding it, 9% increase is 38.5ppt, so it would be seeable on a refractometer for sure if the magnesium affects the reading through the prism in the same way that NaCl does.

Yes. Although I can't tell you exactly what ppt reading he would get. A refractometer measures refractive index which is a dimensionless number. The scales that we have on a refractometer match salinity (psu or ppt) and specific gravity assuming a "standard" composition for sea water. These three do not have a mathematically fixed relationship but can vary with the composition of the water. So, while he might see 38.5 ppt, it might be something less or something more, but he should definitely see an increase.

[sachabballi reef]

I looked very closely and this pod --------> . <---------- seems to have died. I will do a autopsy to see if it had anything to do with magnesium.

ha ha ha....ok Paul good point. 

[Origami]

ha ha ha....ok Paul good point. 

Is that a point? It looks like a period.

[sachabballi reef]

you know, after I typed that I realized some smart alec was going to say something

 

Is that a point? It looks like a period.

 

 LOL

[paul b]

Is that a point? It looks like a period.

Look close, it is a left handed, green eyed, bowlegged pod, and it is dead.

[Origami]

Look close, it is a left handed, green eyed, bowlegged pod, and it is dead.

Awaiting autopsy results. Natural causes or foul play?

 

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[paul b]

Tom, remember that electron microscope I spoke about at your meeting?  I am waiting to borrow that again.

[Integral9]

It was murder and I believe it was professor plumb with candle stick in the study

 

 

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[GraffitiSpotCorals]

I never saw any color change in sps (especially the ones you posted) when treating bryopsis with kent tech m and never had to get it that high.

I am surprised this thread got off topic so quick...

[sachabballi reef]

Im not....

I don't think many people get their mag that high so there isn't much to contribute...hard to argue or agree with no basis

[zygote2k]

Salinity will rise of course through the addition of chloride ions but I was able to counter that by adding less salt. I kept the salinity within 1.024- 1.027 during the whole time.

I never paid much attention to the colors of the corals before but have really noticed the change this round. I'll be looking for a color shift back as the Mg drops.

[Origami]

Salinity will rise of course through the addition of chloride ions but I was able to counter that by adding less salt. I kept the salinity within 1.024- 1.027 during the whole time.

I never paid much attention to the colors of the corals before but have really noticed the change this round. I'll be looking for a color shift back as the Mg drops.

So, if composition of the saltwater, especially trace elements, plays any part in coloration (and I'm not saying that it does or doesn't), then reducing the salt mix naturally reduces the relative trace elements composition at least equally. That is, by 9%. Some people seem to think that potassium may play a part in blue coloration, but it may be internet reefing legend.

 

I think that light and nutrients are the driving factors, though.

 

A thought crossed my mind, just now. With reduced competition from algae, will the zooxanthallae bloom due to increased CO2, nitrates and phosphate availability? Just an idea to think about.

[paul b]

A thought crossed my mind, just now. With reduced competition from algae, will the zooxanthallae bloom due to increased CO2, nitrates and phosphate availability? Just an idea to think about.

 

 

 

Another Idea to think about is that coloration has nothing to do with coral health, it is just a by product of the animals symbiotic algae which may or may not be colorful.  A coral has no "wish" to be, or not be colorful, that is just our wants and in no way reflects on the corals health.

So very healthy corals may not be colorful.  In some corals it could be a sign of starvation in the zoozanthallae.  Corals, unlike many animals do not need to attract a mate.

Many decidiuos trees get colorful in the fall, but that just means the leaves are dying for the winter and the tree will be dormant.

Coral fish are colorful but no one knows why as all deeper water fish appear drab blue in the sea no matter what color they are in our tanks.

Just something else to think about.

 

I took this off of Bora Bora, notice the "colorful" colors of the corals.  This is the natural color of corals.

 

 

 

These pictures on the same reef is partially lit by a flash, so you can see the colors. 

Colors is something we artificially bring out in corals through artificial light. 

 

 

 

Edited September 23, 2013 by paul b

[lnevo]

Interesting observation Paul... Maybe a break thru that the most successful tanks are keeping their corals on the edge of death...kind of like anemones splitting under stress. We may see massive growth or color as a response to something going wrong and maybe explain all the cases of random stn/rtn incidents.. Have to think on this..

[GraffitiSpotCorals]

We artificially ENHANCE corals color with our lights is more accurate.

 

In my experience color shifting and or changing in sps is never good in a tank. We talking about the coral going from colorful to not colorful. Which normally means something is wrong. Paul's talking about corals just not being colorful in general, which his sps may be, but that doesn't really help figure out why the sps corals in this tank started to decline.

[lnevo]

Yeah it was a but off topic but Paul always has a nugget of greatness in his posts

[paul b]

 

 We artificially ENHANCE corals color with our lights is more accurate.

 

 

 

 

 

That is what I meant, the corals in nature exhibit a drab blue color, especialy in slightly deeper water.  When we put them in a 2' deep artificially lit envirnment we expect them to be colorful, even if they were never meant to look that way.  Remember corals don't have any color, it is just the light that penetrates the water and reflects off the coral that allows us to see color.   If the reds and yellows are absorbed into the coral, we will not see those colors, but that just means the coral itself is using that part of the spectrum for itself.  If you look at a red car, it appears red because the paint on that car absorbed the other colors.  A black car feels warm because it absorbed all the colors of the spectrum and all that radiation warms the car.  To me, corals exude health if they overgrow their bases and just keep growing and living forever as most corals do.  Corals don't have a lifespan but keep growing over the old base.  If they die in a couple of years, no matter how colorful they were, they were not thriving.  By the same token, if your reef tank crashes,  (barring mechanical failures)  it was not very healthy because a reef tank should also last forever.  But as was said, if a coral appears colorful, then becames drab, something changed.  Maybe for the better or maybe for the worse.

Just my opinion of course.

[AlanM]

I read somewhere (I think in advanced aquarist article about light maybe?) that the color in corals is due to photosynthetic pigments in the zooanthelle bacteria, which provides energy for the coral polyps. 

 

If the light levels are low, the coral needs higher levels of zooanthelle and lots of pigment together, just like lots of crayons melted together, ends up looking brown. 

 

If the light levels are very high, then the coral needs lower levels of zooanthelle and the coral "bleaches" because those little pigment containing bacteria are not around as much.

 

So to get lots of color you need just the right amount of light.  Not too much, not too little.  And probably just the right levels of Mg and other elements to build up the colored pigments since the skeleton is white regardless, right?

 

Having said that, I've seen pictures of Australian tide pools in Darwin where the corals are in very shallow water and exposed to extremely high light levels.  All those corals were huge, but they looked brown, so who knows.