Magnesium Consumption in a Reef with large SPS colonies?

[AcroporAddict]

Guys,
I have a 300 gallon SPS dominant reef tank. Several of my colonies are dinner plate sized, grown from small frags, so I know there is some decent mag/calcium/KH consumption going on. I have a GEO 818 reactor that keeps up with calcium and KH demand well, but my magnesium levels steadily drop if I don't supplement. System is 425 net gallons. I also have a 150 gallon LPS reef on this system.

Additional equipment is a sulfur denitrator, Nilsen stirrer, Ozone Reactor, GFO and carbon reactors.

I have to add 200 ml of Randy's 2 Part daily to maintain mag at 1350. Otherwise, it slowly drops. I had thought that since the calcium reactor ARM media should have the magnesium in it in normal proportions, that the reactor would provide it in sufficient quanitities.

No major problems in the reef, but I am wondering if my actual biomass of growing corals is doing this to my mag levels? Does the magnesium consumption greatly increase as the colonies get larger and larger? Is this the result of large SPS colony growth in such a limited volume of water? Are the daily additions of Randy's 2 Part normal or not?

Test levels today: KH 8, Calcium 445, and magnesium 1350.

[HighlandReefer]

In a 300 gallon actual water volume system the amount added is about 8 ppm mag per day, which does seem quite high. Water changes with a lower mag level mix can result in more mag to make-up for the salt mix. ;)

[Randy Holmes-Farley]

Are you doing water changes? What salt?

Some reactor media is deficient in magnesium, and people sometimes add some dolomite to the reactor for that reason.

FWIW, the magnesium to calcium ratio is likely the same for a given coral as it grows. But some corals and especially coralline algae consume more magnesium than others.

[pbnj]

But some corals and especially coralline algae consume more magnesium than others.
Cam you identify some corals specifically that are considered high-mag consumers? Can we assume SPS are the most magnesium-demanding?

[tmz]

I assume you are using kalk and it it does not add magnesium . Coraline is a high user . I don't think there is a particularly sps or lps that is a definitive high user. They all use it. Keeping it over 1280ppm is good practice, either by dosing or water changes using a salt mix with sufficient magnesium to meet the needs of the particular aquarium.

Aside from growth some may be lost if abiotic precipitation is occurring in the system.

[Randy Holmes-Farley]

Cam you identify some corals specifically that are considered high-mag consumers? Can we assume SPS are the most magnesium-demanding?


I would not assume that they have a higher ratio (some are very low), but they may grow faster overall.

These articles include some data on magneisum in corals and coralline algae:

Do-It-Yourself Magnesium Supplements for the Reef Aquarium
http://reefkeeping.com/issues/2006-07/rhf/index.php


Magnesium in Reef Aquaria
http://www.advancedaquarist.com/issues/oct2003/chem.htm

[JG1]

I have to dose 30ml of mag a day on my 100g to keep it at 1300ppm. I have maybe 13 frags in the tank but something is consuming the mag.

[HighlandReefer]

Which salt mix are you using?

[Randy Holmes-Farley]

I have to dose 30ml of mag a day on my 100g to keep it at 1300ppm

That's about 4 ppm a day. Pretty high. How much of what are you using to supplement calcium and alkalinity?

A 10% change with 1100 ppm magnesium salt mix will drop 1400 ppm tank magnesium by 30 ppm. So that comes out to 4.3 ppm per day of apparent demand if done once a week..

That's why we often ask about salt mixes. :)

[JG1]

Which salt mix are you using?
Reefers Best Salt

[JG1]

I have to dose 30ml of mag a day on my 100g to keep it at 1300ppm

That's about 4 ppm a day. Pretty high. How much of what are you using to supplement calcium and alkalinity?

A 10% change with 1100 ppm magnesium salt mix will drop 1400 ppm tank magnesium by 30 ppm. So that comes out to 4.3 ppm per day of apparent demand if done once a week..

That's why we often ask about salt mixes. :)

I haven't dosed anything for Calcium or alk for over a month. Even at 10ml a day of two part my Ca and alk were rising to high. My Ca has been around 460 slowly creeping down since the addition of the frags I added a few weeks ago (first corals in the tank). Alk has been maintaing around 7-8dkh on it's own.

[Randy Holmes-Farley]

If you have not needed to supplement calcium or alkalinity, then there is no real demand for magnesium either, and it must be from water changes, or testing error. There is no sink for magnesium that does not use a lot more calcium than magnesium and a lot of alkalinity too.

[JG1]

If you have not needed to supplement calcium or alkalinity, then there is no real demand for magnesium either, and it must be from water changes, or testing error. There is no sink for magnesium that does not use a lot more calcium than magnesium and a lot of alkalinity too.

I'm doing a 5g water change per week. Also, salifert sent me a Ca/Mg check solution and the kit measures within 15ppm of the solution.

I dunno.

[AcroporAddict]

Are you doing water changes? What salt?

Some reactor media is deficient in magnesium, and people sometimes add some dolomite to the reactor for that reason.

FWIW, the magnesium to calcium ratio is likely the same for a given coral as it grows. But some corals and especially coralline algae consume more magnesium than others.

Hi Randy,
Thanks for responding to this. (and thanks to all others). Right now I am using Seachem AquaVitro Salinity salt mix, which is a high quality Salt, IMO, and has lab levels for each batch printed on the side of the bucket. I do 25 gallon water changes every week, so I average about 10% every 2 weeks in my 425 gallon net system. All water is RODI with 0 TDS. I use Salifert test kits for Mag, KH and Calcium, and when I adjust magnesium to 1350 via Randy's 2 Part through the Reef Chemistry Calculator, the Salifert always shows spot on at 1350. I'm a fairly experienced reefer, so I doubt it is test error on my part, and if it is, it is consistent test error.

Calcium Reactor Media is CaribSea ARM large, recommended by GEO (GEO 818). I dose Kalk via a Nilsen stirrer in line with the Tunze ATO. Midwest Aquatics Sulfur Denitrator (which has a very low pH effluent, lower than the Ca reactor).

I thought adding magnesium media to a calcium reactor was useless, as the magnesium media needed a much lower pH to dissolve than regular calcium reactor media? Didn't you suggest a separate magnesium reactor for that type media?

I really appreciate your input. I don't want to think I have an issue if I don't. This is just an aspect of reef chemistry that I don't understand too well. The biomass of the corals in my 300 gallon reef is so much more than it was a year ago. Not complaining, but I wonder how or if the mag/Ca/KH demands of a reef with large colonies is different from one with all small frags or smaller colonies, particularly given that the size of the colonies are always increasing, but the volume of water they are in is always the same?

Could the Sulfur Denitrator have anything to do with the magnesium depletion?
Dave

[RyanAlan]

Do you happen to have an mangroves incorporated into your system?

[AcroporAddict]

Do you happen to have an mangroves incorporated into your system?

No mangroves...just a cheato refugium.
.

[jdm1114]

I am also having issues with alot of magnesium consumption. I use the same salt as (acroporaddict). I also have cheato in my refugium along with other types of macro algae. I use fully saturated kalk for all my evaporation and b-ionic 2 part to cover the rest of my calcium and alkainity consumption. I use 60ml of each part daily. I do 20 percent water changes bi weekly. My total system water volume is around 250 gallons. My system is thriving with mostly sps colonies.

I am not trying to hi-jack this thread I just want to keep it going. Could my addition of kalk to cover all my evaporation needs be eating up my magnesium some how? My kalk addition is by ato, and is around 2 gallons a day.

[jdm1114]

My parameters are:

Calcium: 420ppm
Alkalinity: 3 meq/L
Magnesium: 1200ppm

[AcroporAddict]

Welcome aboard jdm1114.......the more the merrier.

I doubt that it is magnesium depletion via water changes because Aquavitro Salinity is consistently at NSW or above levels IME. SeaChem kinda dominates the local salt markets here because they are HQ'd very close to Atlanta, where I live.

I'll tell you a story that testifies to the quality of this Salinity: I have a 100 gallon reef with a calcium reactor that had developed a leak in the bubble counter keeping any CO2 from getting into the reactor. It was a good 5-6 weeks like this. I tested weekly during this time and my calcium was consistently 440+, KH 8-9 and magnesium 1300+. I had been doing slightly more frequent than normal water changes with Salinity during this 5-6 week time with a non-functioning calcium reactor, but my testing was all normal levels, thanks to the Salinity.

But if Randy could address the comment I made about magnesium media needing a much lower pH to dissolve that calcareous ARM type Reactor media, I'd appreciate it. If this is untrue, then I'd certainly add some dolomite or whatever to keep mag levels up.

I also do not have a lot of precipitate type calcium deposition in my tank that I can see.

[Randy Holmes-Farley]

Could my addition of kalk to cover all my evaporation needs be eating up my magnesium some how?

No, it does not appreciably deplete magnesium, but it doesn't supply any either, so you are supplying calcium and alkalinity, but no magnesium, and as corals and abiotic precipitation use it up magnesium by incorporation into calcium carbonate, magnesium will slowly decline. :

[Randy Holmes-Farley]

Right now I am using Seachem AquaVitro Salinity salt mix, which is a high quality Salt, IMO, and has lab levels for each batch printed on the side of the bucket.

Ever actually test it? At the salinity you use in your tank?

Dolomite in a CaCO3/CO2 reactor is a fine plan. :)

Sulfur denitrators won't impact magnesium.

[AcroporAddict]

Could my addition of kalk to cover all my evaporation needs be eating up my magnesium some how?

No, it does not appreciably deplete magnesium, but it doesn't supply any either, so you are supplying calcium and alkalinity, but no magnesium, and as corals and abiotic precipitation use it up magnesium by incorporation into calcium carbonate, magnesium will slowly decline. :

OK then, that is something I think I can understand.
I dose some calcium, alkalinity and magnesium through my calcium reactor, and add calcium and alkalinity (but no mag) through my Nilsen stirrer.

My calcium reactor is dialed in at a certain KH, but that dial-in is also influenced by the percentage of total alkalinity and calcium the kalk I am adding contributes, meaning that if I removed the kalk addition, I would probably have to adjust my calcium reactor to produce more calcium and alkalinity to make up for the removal of the kalk.

In that situation, with only a calcium reactor adding calcium and KH to the system, we would probably not see this magnesium decrease (or much less of a decease), as it would probably be added in normal ratios to calcium and KH from the reactor media.

[Randy Holmes-Farley]

The CaCO3/CO2 reactor can still often deliver solutions deficient in magnesium. That is why many reefers use dolomite as a portion of the reactor media.

[jdm1114]

Could my addition of kalk to cover all my evaporation needs be eating up my magnesium some how?

No, it does not appreciably deplete magnesium, but it doesn't supply any either, so you are supplying calcium and alkalinity, but no magnesium, and as corals and abiotic precipitation use it up magnesium by incorporation into calcium carbonate, magnesium will slowly decline. :


Alright that makes sense, thank you.

In my situation what is the best way to add magnesium. I have been adding it with BRS 2 part in a 7:1 ratio, (chloride:sulfide). I cant seem to keep my mag above 1300ppm.

[AcroporAddict]

The CaCO3/CO2 reactor can still often deliver solutions deficient in magnesium. That is why many reefers use dolomite as a portion of the reactor media.

Would you recommend keeping the dolomite separate in the Ca reactor, like in a filter bag, so you can tell what is what?

Or maybe a secondary reactor for the effluent to flow through, like the second chamber in a calcium reactor, just filled with dolomite?

[Randy Holmes-Farley]

The BRS product is a fine way to boost magnesium. If you seem to have trouble keeping it up, and trust your kit, just add more. :)

As to separating the dolomite, I do not think people usually do that, but some may. It is usually in the same reactor, around 10% dolomite, IIRC.

[AcroporAddict]

Thanks for all your help Randy. As usual, I greatly appreciate it!
Dave

[jdm1114]

[QUOTE=Randy Holmes-Farley;18612758]The BRS product is a fine way to boost magnesium. If you seem to have trouble keeping it up, and trust your kit, just add more. :)

Alright thank you for the fast reply, should I keep dosing at the 7:1 ratio of chloride:sulfate or should I bump it up to a 10:1 ratio?

[Randy Holmes-Farley]

I'd use 10:1 unless you also use calcium chloride. :)

Thanks for all your help Randy. As usual, I greatly appreciate it!


You're welcome.

Happy Reefing. :)

[jdm1114]

Alright great, thank you Mr. Farley.

The only calcium chloride I use would be in my b-ionic two part. Which is used to cover the remainder of my calcium and alkalinity needs not covered by my fully saturated kalk which is added via ato. I use 60ml of part A and part B daily. Would this be enough to keep my chloride to sulfate ratio at 7:1?

[HighlandReefer]

Mag Supplementing Recommendations:

Mag sulfate and mag chloride are both important when increasing and/or maintaining your mag level. The mag sulfate will increase your sulfate whereas mag chloride will increase your chloride in your water. The idea is to keep the sulfate and chloride in balance in your water column. This leads to using them in the proper ratio to maintain the proper balance.

Randy calculated the ratios to maintain the proper balance of chloride to sulfate. It will depend on what you are using to maintain your calcium with.

---------------------------------------------------------------------------------

If you are using Calcium chloride (two-part) to maintain your calcium, then use:

5 cups of mag chloride + 3 cups of mag sulfate in a total of one gallon with rodi water. Mix and you can add the particles in the solution.

An Improved Do-it-Yourself Two-Part Calcium and Alkalinity Supplement System
http://reefkeeping.com/issues/2006-02/rhf/index.php


----------------------------------------------------------------------------------

If you are using kalk water or reactors to maintain your calcium, then use:

7.25 cups mag chloride + .75 cups of mag sulfate.

Do-It-Yourself Magnesium Supplements for the Reef Aquarium
http://reefkeeping.com/issues/2006-07/rhf/index.php

-----------------------------------------------------------------------------------

If you want to bump up your mag level in your tank or you want to increase the mag level in your salt mix or natural seawater, then use:

7.25 cups mag chloride + .75 cups of mag sulfate.

This is perfectly balanced with what is found in sea water and does not take into consideration any additions of chloride from calcium additives.

Do-It-Yourself Magnesium Supplements for the Reef Aquarium
http://reefkeeping.com/issues/2006-07/rhf/index.php

-------------------------------------------------------------------------------------------

If you are using reactors (and/or kalk water) and also supplement with calcium chloride, then perhaps a good ratio to use would be:

7 cups mag chloride + 1 cup mag sulfate. :)

[jdm1114]

Great thank you, I guess that means I was doing things right all along. I just need to check my test kit for accuracy. I am using a seachem mag test kit.

[AcroporAddict]

I just bought two containers of Brightwell Aquatics Neo-Mag to add to my GEO 818. Brightwell recommends a 9:1 ratio Neo-Mag to Calcareous media to start. Gonna do this and discontinue the liquid mag supplementation and see what happens.
Dave

[travis32]

Someone asked about mangroves being in the tank? I'm curious, why would you ask about mangroves in a magnesium issue? The reason I ask is I have 6 mangroves doing o.k. in my 125g (they're in the sump.), and I too recently discussed magnesium issues maintaining my calk with limewater. Based on my testing I am anywhere from 4 to 10ppm magnesium usage per day. In previous discussions with Randy I'm experimenting with not dosing mag and not testing for 1 month.

If mangroves use it or deplete it faster? That would be an interesting part I missed before.

[Randy Holmes-Farley]

Some people think mangroves pull substantial magnesium from the water. I've always been somewhat skeptical when there is just one or two small plants. They may excrete magnesium salts from the leaves, but if that is allowed to drop back into the tank, magnesium won't go down like it might if it drips outside the tank.

In any case, it may be a sink for you, especially if you have a lot of them or they are big.

[AcroporAddict]

I just bought two containers of Brightwell Aquatics Neo-Mag to add to my GEO 818. Brightwell recommends a 9:1 ratio Neo-Mag to Calcareous media to start. Gonna do this and discontinue the liquid mag supplementation and see what happens.
Dave

Sorry guys, I had the ratio backwards. 1 part Neo-mag to 9 parts calcareous media.

[travis32]

Some people think mangroves pull substantial magnesium from the water. I've always been somewhat skeptical when there is just one or two small plants. They may excrete magnesium salts from the leaves, but if that is allowed to drop back into the tank, magnesium won't go down like it might if it drips outside the tank.

In any case, it may be a sink for you, especially if you have a lot of them or they are big.

They're each about 6" - 10" tall, they haven't formed leaves yet, but, they've been growing roots. all of them have nice about 2 - 4 " roots growing nicely. I may have lost 1 of the six. As it's root was black, but, It's stem is still green, so, I'm going to see if it comes back or not.

But, I got the nitrate absorbing mangroves. So, I didn't realize they would deplete magnesium. Maybe my magnesium is going somewhere! ;)

EEK!

[Randy Holmes-Farley]

Well, see. :)

[RickMartin]

Did anyone test their salt mix yet? I am curious what the tested mag levels in the salt are at.

[AcroporAddict]

Did anyone test their salt mix yet? I am curious what the tested mag levels in the salt are at.

I will test the levels in my Salinity salt mix.

[jdm1114]

ACROPORADDICT can we see some pictures of your tank?

[AcroporAddict]

Here are my test levels of Salinity at SG 1.026. I don;t have the "certified results" on the side of the container any more because this salt was in a 300 lb Balrel (largest size of Salinity you can buy). I had to open it and put it into several smaller buckets to get it home!

SG 1.025
Mag: 1140
Ca: 400
KH: 8.0

All test done with Salifert Kits.

[AcroporAddict]

ACROPORADDICT can we see some pictures of your tank?

Here is a video done by a friend of mine a couple months ago. Tabling colonies are a bit larger now.

http://www.youtube.com/watch?v=_KJoHx4s_hQ&feature=player_embedded

The Vortechs on the left/right sides are the 7500 gph MP60s with two 3200 gph MP40wES units on the back. Radium 400 watt halide lighting.

[RickMartin]

Nice tank!!
low Mg from the salt mix is probably the reason you are having to add so much.

[jdm1114]

very nice tank

[DarkXerox]

Here are my test levels of Salinity at SG 1.026. I don;t have the "certified results" on the side of the container any more because this salt was in a 300 lb Balrel (largest size of Salinity you can buy). I had to open it and put it into several smaller buckets to get it home!

SG 1.025
Mag: 1140
Ca: 400
KH: 8.0

All test done with Salifert Kits.

This is why I don't put much stock into their batch analysis. Homogeneity could also be an issue due to settling during shipping. Did you mix the original container before aliquoting into smaller containers?

[AcroporAddict]

Guys,
It has been about 4 days since I added two containers of Brightwell Neo-Zeo magnesium calcium reactor media to my GEO 818 and discontinued the 200ml daily dose of Randy's 2 part. I'm at about 8.5-9:1 ARM Media to Neo-Zeo. Left all calcium reactor controller settings the same initially. I have since had to raise my controller setpoint because my Mag, Ca and KH became slightly elevated. Mag was at 1470 yesterday. I raised the controller setpoint by .3 units of pH, and today the mag level was 1350. I'll play with that until I am keeping all params in normal range. But I would say the Neo-Zeo really does help magnesium levels at regular Calcium Reactor settings, because after 4 days without any 2 part , the mag levels would probably be 1150-1200.

I am really impressed so far with this Brightwell Neo-Zeo. Only trick now is to find the right ratio of it to ARM media to balance out the readings. Brightwell recommends no more than a 1:7 Neo-Zeo to ARM ratio at the most.