replenishing magnesium

[danny zubot]

Here's something interesting. I checked my levels last night and I got this:

Ca+ 450 ppm,
Mg 1220 ppm,
ALK 7.87 D-KH

I won't be adding any Ca+ because its a bit higher then I usually keep it. I may buffer a bit for ALK, but here's what I've noticed thats interesting. Growth in my corals has really slowed down in the past couple of weeks that my Ca+ has been high (oops). Tonight I'll add Mg to bring my levels back up to 1280-1300 ppm and see what happens. Incidently, its taken two weeks for my Ca+ to go from 485 to 450 ppm, probly as a result of lower Mg levels.

Another note: according to the calculator it will take 304 grams of Seachem Mg (60.8 tsps), and 346 Ml of Kents to achive the levels I want. That seems like a lot to me.

[Beverly]

Originally Posted by danny zubot

Another note: according to the calculator it will take 304 grams of Seachem Mg (60.8 tsps), and 346 Ml of Kents to achive the levels I want. That seems like a lot to me.

Going way back in my notes for my 37g, I had 1185 ppm of Mg when I began testing. The calculator sugggested I add 321 ml of Kent's Tech-M Mg.

Don't know what you mean by "346 Ml of Kents". If it is some kind of buffer, remember when using the calculator, the calculator measures alk in meq/l, dKH and ppm. You have to select the right measurement from the three choices. Many times I have forgotten to select dKH instead of the default meq/l and ended up with a horrendous amount of buffer I had to add. Luckily I remembered to double check.

[danny zubot]

Well Tech-M by Kent is the only option it gives you for Kent products. I believe that "ppm" is the only option it gives you for Mg calculations as well. That dosage just seems like a lot to me, though I don't have measuring cups in front of me right now for reference.

[Beverly]

Ooooooohhh, now I know what you are talking about - two types of Mg supplement - one being Kent, the other Seachem Geez, some people are just naturally slow Don't know anything about Seachem's product, only Kent's.

Yes, Ca and Mg on that calculator are measured only in ppm, as you state. Alk has the three measurements from which to choose.

Danny, a couple of things to consider here:

1. Did you use the tank volume calculator using inside measurements for an accurate volume of your tank?

2. Don't dose the Mg supplement all in one day. Spread it out over 2-3 days. For instance, I use a 10 ml plastic syringe for dosing so I can record how much I dose at a given time. In my 37g (which has a volume of only 35.5g according the volume calculator), I add 30 ml at a time. I might dose every 1-4 hours throughout the day, depending on what my day is like.

3. Measure Mg at some point to while dosing to see if you are actually overdosing or on target.

4. Record all test results and how much of what you dose so you can go back and observe patterns of use of alk, Ca and Mg. I also record pH before and after dosing (for buffers), time of day, and occasionally nitrate.

Dang, that's more than a couple of things, now isn't it

[danny zubot]

Yah, its a lot of work but thankfully I have a new log book for th is tank. I'm pretty sure my system volume is acurate to within 2 gallons, or a days evaporation. I'll adjust tonight and measure a couple hours after.

[dirtyreefer]

Originally Posted by StirCrazy

Well its a balance game, to make a stupid analogy would you want to walk on a ledge 2" wide 6000 feet in the air or would you want to walk on a ledge 5 feet wide? in other words why ride that close to problems (depleted Ca, low Alk) when you can have it at a proper level and have a cushion area be for these things happen?

Steve, I know exactly what you're saying and thanks for the good analogy

I guess you could sort of compare what Mg is to Ca as KH (alk) is to pH as it acts as a buffer for the other.

But I guess what I'm wondering is, let's say I test my Mg and it's at a little lower than desired levels (e.g. 1000ppm), and I purchase something to bump it up to 1400, would I see a difference in my corals? Will I see better color, better growth? Or am I just making sure my Ca doesn't crash?

[StirCrazy]

Originally Posted by dirtyreefer

and I purchase something to bump it up to 1400, would I see a difference in my corals? Will I see better color, better growth? Or am I just making sure my Ca doesn't crash?

if you take it to say 1300, And keep your Ca down about 380 to 400 I feel you get better growth, is this to say if you do the same you will to? well maybe, or maybe not. I would bet all things being equal that you would dee a difference it may be small but I think there would be one. Also it is the same a a sick person, they may look fine on the outside but not inside. so theres another thing to think about sence so little is actualy knowen about coral helth.

Steve

[danny zubot]

But I guess what I'm wondering is, let's say I test my Mg and it's at a little lower than desired levels (e.g. 1000ppm), and I purchase something to bump it up to 1400, would I see a difference in my corals? Will I see better color, better growth? Or am I just making sure my Ca doesn't crash?

IMO you don't want to super load your tank with any one substance. Mg is a slowly depleting element in a reef, much more so than Ca and Alk etc. If you add too much Mg (which we know is needed to make Ca bio available) you run the risk of precipitating the access Mg with Ca+ in you system, and will cause your Ca levels to drop faster. This was noticed in my tank once as aragonite turning into rock. I don't believe it is harmful to your corals, but it is a waste. I would keep your Mg at the high end of normal, around 1350 ppm, at this level your corals can best optinimize Ca consumption at around 350 to 400 as stated above.

When my Mg levels are down I noitice less Ca consumption when testing, which coralates to less coral growth. Hope this helps

[StirCrazy]

[quote="danny zubot"]

IMO you don't want to super load your tank with any one substance. Mg is a slowly depleting element in a reef, much more so than Ca and Alk etc. If you add too much Mg (which we know is needed to make Ca bio available) you run the risk of precipitating the access Mg with Ca+ in you system, and will cause your Ca levels to drop faster. This was noticed in my tank once as aragonite turning into rock. I don't believe it is harmful to your corals, but it is a waste. I would keep your Mg at the high end of normal, around 1350 ppm, at this level your corals can best optinimize Ca consumption at around 350 to 400 as stated above.

When my Mg levels are down I notice less Ca consumption when testing, which correlates to less coral growth. Hope this helps

couple things, Mg doesn't make Ca "bio available" if you read the articles Bev have been posting every chance she gets I believe there is one that explains how Mg works in great detail, if not ask and I will find it and post it. but for a short version Mg simply coats Ca to prevent other stuff from bonding to it and dropping it out of solution so with out the proper amount of Mg Ca will participate out of solution. I guess if you want to say that makes it Bio available in a round about way it could be but it is a very misleading statement.

Also normal Mg levels are 1300 to 1400 ppm so 1350 is dead middle. there have been some tests done on higher Mg levels and it becomes a mute point after the "normal" range and it will take a much higher level to cause harm as nothing will use Mg except for the Ca ions themselves, but having said this I don't want people just to dump indiscriminately to raise Mg, always measure and raise it no more than 200ppm / day or so.

Steve