Great article explaining water chemistry

[jrgilles]

Set up my first reef tank about 7 months ago, so a bit of a noob with the chemistry.

I knew the basics, but this article made it all clear. Its very well written and explains the balance between alk, ca, and mg and how they all work together.

Thought I'd share my find:
http://reefkeeping.com/issues/2002-04/rhf/feature/index.php

 

[Boomer]

That article is under the sticky's "Reef Chemistry Articles" with allot more like it.

 

[jrgilles]

OK, awesome. I'll read through them. I have a lot to learn. Trying to get my chemistry in check, but it seems everything I do is adversly affecting other parameters.

A week ago I had:
Ca: 400
Mg: 1100
Alk: 9 dKH

Over the week I dosed:
1 day of max Ca (2 tbsp in 4 pints of water for my 120 gal system) from my SeaChem Ca powder
Then I dosed 3 days of the max Mg (also seachem, 1 tbsp per day in 3 pints of water.)

I just tested yesterday, and I'm now at:
Ca: 390 (starteed a kalk drip)
Mg: 1150 (about what I expected)
Alk: 7 dKH.

So apparently my Alk has now dropped way down, almost to what I think is dangerously low levels. My green Hydrophora is no longer inflated.

So, last night I dosed the max daily alk (Seachem Reef Builder), 2 tbsp in 5 pints of water over the corse of the evening.
And I put in another tbsp of alk disolved in 4 pints of di water this morning.

I'll continue to try to raise alk over the next couple days, then retest everything.

Hopefully this will get things in check. pH has been sitting around 8.0 to 8.1, as read on a pH probe, so somewhere around 8.15 to 8.25 'Natural Seawater pH'

Salinity is holding stable at 1.025.

Do you see anything glaringly wrong with what I'm doing?

I was very suprised to see the KH drop so low, as I've never seen it that low before.

 

[Boomer]

Do you see anything glaringly wrong with what I'm doing?...............................Mg: 1100

You have a testing error here, it cannot be that low. Seawater is 2800 ppm Mg++

I was very suprised to see the KH drop so low, as I've never seen it that low before.

Your Ca++ went for 400 to 390. That means tha Alk must drrop at least 1.4 dKH. For each drop in Calcium of 20 ppm the dKH drops 2.8 dKH. Your Alk was 9 and went to 7. 9-7 = 2 and 2 - 1.4 = 0.6 dKH that want to other reactions that do not evolve Calcium. So, this is quiet normal.

So apparently my Alk has now dropped way down, almost to what I think is dangerously low levels

Nope not so at all. That 7 dKH is still higher than NSW, which is ~ 6.5 dKH. Most just like to run it higher ~ 9 or so.

 

[jrgilles]

alright, thanks a lot. Makes me feel better. I will recheck the calculations/instructions on the Mg test. I'm guessing it is most likely a user error.

It is an elos test kit, and I'm guessing I used the wrong factor (I used

[drops from part 1] - [drops from part 2] * 50.

From looking on the internet, I'm guessing either I'm using different units than ppm, or I used a wrong factor.

It appears each drop is 100 ppm, but I'll have to check when I get home. If that were the case, I'm at 2300 ppm (instead of 1150). So I'll continue to increase the mag.

Thanks for the reply boomer, appreciate it.

 

[Boomer]

WOOPS big error on my part

It is 1300 ppm Mg++ NOT 2800 ppm. That is for Sulfate :lol: So, that is not an error on your part. You are low about 200 ppm. It is safe to add 100 ppm / day.

 

[DonW]

WOOPS big error on my part

It is 1300 ppm Mg++ NOT 2800 ppm.

Back to the home for your nap.


Don

 

[Boomer]

You are still alive Don

 

[jrgilles]

Awesome, thanks for correcting that. I'll get Mg at the right level first while the kalk drip is going (on a controller adding periodically at night as long as pH requirements are met).

Then I'll check in a few days, and I bet the dKH will be right back where it should be with what I've dosed already.

The more I learn about this chemistry, the more I realize that I need to do a lot more research. I'll check out all the articles in the stickies in this forum. I have a chem minor too, go figure. All the interactions here are pretty complicated and seems there are a lot of common intermediates that make it not as intuitive as my original view. Thanks for the help.

 

[DonW]

Awesome, thanks for correcting that. I'll get Mg at the right level first while the kalk drip is going (on a controller adding periodically at night as long as pH requirements are met).

Then I'll check in a few days, and I bet the dKH will be right back where it should be with what I've dosed already.

The more I learn about this chemistry, the more I realize that I need to do a lot more research. I'll check out all the articles in the stickies in this forum. I have a chem minor too, go figure. All the interactions here are pretty complicated and seems there are a lot of common intermediates that make it not as intuitive as my original view. Thanks for the help.

Your alk is actually ok. If you want it up along with your Mg then do a good sized water change. Its going to take way to much Mg additive to bring it up 200ppm. Its more cost prohibitive to just do a big water change and kill more than one bird with one stone.

Don

 

[jrgilles]

Yea, I'm using instant ocean salt, which I think is part of the problem. Its just not putting in the amount of Mg I need.

I'm going to have to research different salt and switch to something better after this bucket is gone.

 

[DonW]

Yea, I'm using instant ocean salt, which I think is part of the problem. Its just not putting in the amount of Mg I need.

I'm going to have to research different salt and switch to something better after this bucket is gone.

Its easier to balance you salt than get a tank back on track. Check out bulk reef supply. Their mg shoud take about 150ml per 5g waterchange with IO. With CA 50 ml per 5g to get it to 400. Mg depleats so slowly you shouldnt need to add to the tank unless your relaxed with water changes or dont balance your new water.

Don

 

[jrgilles]

I've been changing water out 15% every week, so don't think I've been too lax.

I think I was messing things up though, as I was adding ca and mg to 30 gal DI water. Waiting 24 H, then adding alk supplement, (which probably precipitated everything I added), mix 24H, then adding salt, and mixing 24 H.

But yea, I think I was just precipitating things, as I see a visible coating on the outside of my mixing bucket.

I'll start just adding ca and mg and leaving alk alone, or adding to the tank midway between water changes if I end up needing it.

Its all becoming clear now.....

 

[Xtremedave67]

jumping on this thread I need this info, and thanks Rob that article will help me