Reef Adv Mg in topoff water?

[snorkeler]

Hello, I'm thinking about dissolving Seachem's Reef Advantage Magnesium crystals in my auto-topoff RO/DI water as a way to automatically dose magnesium into the tank.

Is this a reasonable approach? Would this work, any pitfalls in your opinion?

Thanks,

Snorkeler (Fabio Paoli)

[bertoni]

It's a reasonable approach, but most tanks consume so little magnesium that the approach doesn't save much effort, assuming a reasonable water change schedule. I might have had to dose magnesium every six months or so.

[snorkeler]

Thanks Bertoni. My tank,Ii'm not sure why, seems to consume a lot of Mg... and I hardly have any corals in there.... every time I leave it alone for a while then measure it is is below ideal concentrations. Sometimes much below.... that's why I was thinking of using ATO to compensate this consumption.

[snidelywhiplash]

I use Carribsea aragaMIGHT! it has all the trace elements and has worked very well

[jason2459]

What is your calcium levels? Could it be that what ever it is that is consuming the Mg so much might be because the calcium levels are two low?

[snidelywhiplash]

Do you have alot of coraline algae? I've heard (plz correct me if wrong) that it consumes mg

[snorkeler]

I have to test Ca as I'm not sure where it is at now, but in the past it was at borderline lower OK limits. I do have Coraline but can't say too much Coraline.

Snorkeler

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[snorkeler]

Just measured water parameters and they don't look very good, Alk, Ca and Mg low:
pH = 8.4 (fine)
Alk = 5.6dKH (low < 7dkH)
Ca = 350ppm (low < 420dkH)
Mg = 875ppm (very low < 1250ppm)

I added Alk buffer (Red Sea Coral Success Buff), enough to rise Alk by 1.4dkH, will measure again tomorrow.

Now I need to get some Ca buffer at the LFS. I have Mg buffer but I don't want to spend it until I've raised Ca levels first as Mg takes so long to raise ($$)....

My Alk consumption, after I implemented continuous automatic WC (described in thread http://www.reefcentral.com/forums/showthread.php?t=1917235) seems to be 0.2dkH/day . I have no SPS and only one LPS.... small.... Not sure if that consumption is because of the Coraline or because Ca is so low right now... yes, probably that is the cause.

Snorkeler

[snidelywhiplash]

Don't raise alk too fast!!! imo that could be detrimental.. You're on the right track! I've been told mg level can affect how much usable alk and ca are in the water.. I would say look into a calcium reactor and if you take the plunge get some neomag by brightwell to add in as it rocks for keeping mg levels up

[podman1973]

i have coralin alge all over my tank and my mag is a bit more diff. to maint. I just started to use doleamite in my cal. reactor hop it takes care of the problem

[bertoni]

All calcifying organisms will consume some magnesium, and some coralline algae can create deposits with 5% of the calcium replaced by magnesium, for example. That level is very low, and I'm not sure that I believe it. I'd try measuring some freshly-mixed saltwater. If the level is that low, the tank will require a huge amount of supplement to get the level back to 1260 ppm. This calculator might help:

http://reef.diesyst.com/chemcalc/chemcalc.html

For example, I get 21 fl oz of Kent Tech-M to raise the level to 1260, assuming there's 30 g of actual water in the system. The recommended dosing limit is 100 ppm per day, and I'd target less than that for the first dose, unless you're very sure about the total water volume.

Once the test kit has been verified, and the level is back to 1260 ppm, it should stay there unless water changes are done with a low-magnesium salt mix.

[snorkeler]

I never thought about testing my new SW, that's a good idea. I'm using Red Sea so it should be OK, but it is better to test it just in case, you're right.

The test kit is a Seachem Reef Status, which should be very precise.

Snorkeler

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[snorkeler]

I tested my new SW and wow, is it low in everything.... I'm having a hard time believing the results, but I know I followed testing procedures correctly.... the new SW I tested was not recently mixed, it has been in the (covered) mixing container for at least a week. Could the container have absorbed Ca and Mg? I have noticed a type of slime growing in the container, covering walls and rubber parts (like powerhead fixture suction cups), could that be something alive absorbing Ca and Mg from the water?

The parameters of the new SW I tested were:
Ca=350ppm
Mg=875ppm
Alk=5.6dKH=2meq/L
pH=8.4 (only good parameter in fact)

I'm using a 20Kg bucket of Red Sea salt, which I mix at the proportion of 33g of salt for 1Kg of water (targeting 1.032 salinity). That would be 1Kg for salt for 30.3Kg of water (very close to Red Sea's recommended ratio of 1Kg of salt for 30L of water to reach an Alkalinity of 2.2to 2.5meq/L). I use RO/DI water.

The bucket is about 9 months old now, but has remained closed when not in use. I still have some 7Kg in there, I estimate, would hate to have to dump it....

Pointers?

Snorkeler

[bertoni]

Wow, I'd get second opinions on the test kits and on the SG. The salt might have settled, so mixing up any dry portion remaining might help.

[snorkeler]

Just noticed a typo: I target 1.023 SG not 1.032 as I wrote.

Sometime this week I'll take my new SW to be tested at the LFS.

Snorkeler

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[jason2459]

bumping your SG up to 1.026 would help bring up the numbers a bit. No reason not to.

[bertoni]

I would raise the SG to 1.0264, too, although I'd do it slowly, over a couple of weeks or so.

[snorkeler]

I tested my new SW today, Red Sea mixed with RO/DI at 36ppt.
Ca=400ppm (low)
Mg=938ppm (very low)

I must say I'm a little disappointed... I don't think I'll repurchase Red Sea salt when the bucket finishes.

Anyway, I added 10ml of Eco Mg to the new SW mixing container (42L) before taking water for a WC.

Snorkeler

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[bertoni]

Wow, that's low! Have you double-checked the test kit? Testing failures are fairly common. That's just very, very low.

[snorkeler]

No, you're right, maybe I should do that too. The test kit has a 1300ppm sample for testing itself, so it won't be too difficult.

[snorkeler]

I just tested the kit.... using the 1300ppm sample it includes for testing.... and it tested at 1125ppm....

I am very sure I'm following correctly the testing procedure, I read and re-read the instructions many times in the past and even now. I am carefully measuring the titrate in the syringe, looking at titrate level position not at plunger level position to discover how much I dripped into the test mixture (because between titrate and plunger there is a little bit of air always).

So, what should I do? Apply a 1.16 (=1300/1125) correction factor to readings, or, dump this test kit altogether?

This is discouraging... if I can't trust test kits, what can I trust? This is supposed to be a high quality test kit, Seachem Reef Status... it isn't old, I bought it in December 2009 and did maybe some 30 tests up to today.

Thanks for the pointers.

Snorkeler

[bertoni]

I would ditch the kit. There's no way to know what kind of correction factor would be useful, if any.