troubleshooting alkalinity

[kwirky]

I think I have it solved! Finally!

So i've been using Oceanpure salt, which is a great price, and it's loaded with everything. Mixes nice and fast. Only thing is I've got a strange hardness thing going on now.

Here are my water parameters:
temperature 80.2-4
specific gravity 1.025
120ppm CaCO3 (calcium carbonate) (6.72 dkH, 2.4 meq/L)
440ppm calcium.
whopping 1650ppm of magnesium.

So it's high in everything, INCLUDING magnesium. I'm suspecting my batch, since googling it, most everyone else gets 1350 ppm magnesium.
update: a bad batch has been ruled out

Here are some good readings I've found, which I think I should share.

reading on relationship between calcium and calcium carbonate:
http://www.advancedaquarist.com/issues/nov2002/chem.htm

reading on magnesium:
http://www.advancedaquarist.com/issues/oct2003/chem.htm

CaCO3 to meq/L to dkH converter
http://www.saltyzoo.com/SaltyCalcs/AlkConv.php

My pH fluctuates in VERY strange ways. I initially figured it to be unpredictable, but now that I've learned of magnesium's interference with the precipitation of CaCO3, it's very predictable.

saltwater with double the natural concentration of magnesium doubles the time it takes for CaCO3 to precipitate. Magnesium attaches to the newly forming CaCO3 crystals, inhibiting it's crystaline growth. So when dosing kalkwasser, the calcium is added right away, but the CaCO3 isn't. So that explains why my pH wouldn't raise until about 20 hours after the dosing of the kalkwasser. I was noticing my pH RAISING at night, rather than dropping.
update: I got this mixed up. It slows the precipitation of CaCO3. Meaning it slows the drop in your alkalinity. Am I right?



So the magnesium was preventing the calcium carbonate to form at the same pace at the calcium, I predict that since calcium had 20 hours to "have it's way" with the imballanced CaCO3, causing the alkalinity to drop further.

I've just been having wierd stuff happening.

Water changes are out of the question to correct the problem, because I tested a new batch of saltwater with the mix, and it tested high in magnesium as well. I don't want to blow money on another bucket of salt, since that high of a magnesium concentration would require a very wasteful water change. I'd rather try to fix it.

So I'm going to try adding baking soda. the formula is:
for 50 gallons of water
1 teaspoon of baking soda
raises alkalinity by 0.4 meq/L (~1dkH)

my target is 3.0 meq/L of alkalinity, so I'll be adding 6 tsp's of baking soda through a slow 24 hour drip.

I'll post my results.

[Moogled]

So like...French chicks have hairy pits, right?

<boggled by chemistry>

[albert_dao]

I think you read the article wrong Sean.

How does magnesium impact the balance of calcium and alkalinity23 in reef aquaria? In order to answer that question, one has to have a basic understanding of the calcium and carbonate systems in seawater. These systems have been discussed in detail in a variety of previous articles, so I won't go into them here in great detail. In short, calcium carbonate (CaCO3) is supersaturated in seawater,24 meaning that given enough time calcium ions will interact with carbonate ions and precipitate as calcium carbonate. If you push the concentration of either too high, CaCO3 will start to precipitate. Magnesium interferes with this process, permitting both calcium and carbonate to be elevated above where they would be in the absence of magnesium.

It's not preventing the carbonate from forming, it's preventing it from precipitating from the water.

[littlesilvermax]

That is really weird. Why I really like to use ION and then supplement the magnesium and caclium myself.

Any chance your SG is off and maybe higher then you think? Do you have a calibrated refractometer?

[support@proline]

Hi Sean

I like to help you troubleshoot your system to see what could be the possible cause of your PH swings ,however first I like to clairfy a few things

1-Ocean pure Pro is designed for more demanding tanks & is fortified with all the elements so you don't have to dose anything to balance the salt mix
2- I did contact manufaturer this morning after reading your post ,there has been no reports of a bad batch ,I even provided him with the batch number of the products that we have distributed in the west coast in the past 3 months & no reports.
keep in mind each salt batch is in kilo tons ,therefore if there be any problems it will be all overplace ,CANADA ,US ,EUROPE & ASIA.
3- Your MG reading is abit high however even @ that point you will not have any IONIC Balance distruption of any sort AS YOU MIGHT THINK.

4- This is the same salt I am using on my own system & many other people here & calgary with no repoted problems.

Now back to the possible cause of your PH SWING
1- As far as the chemistry
I think Albert hit the spot ,what I am getting from your post your are complaining that the extra MG is not allowing the formation of the CACO3 crystaline solid,well you do not want the recalicification happen in your water column any way ,i could not understand the point there?

2-Also you do not have any free radicals in your water so when they say the concentration of a certain element that means the available Ions of that element that are balanced in the mix ,if you mix your salt with water you do not have CA+2 IONS free in the water ,it is in your solution balanced with the positive Ions of the same but opposite charge.
so I can not understand the relation you are trying to make between the readily available CA & CACO3.

3- I have thought hard how 300 ppm more of MG in the mix can be the cause of PH swingsbut didn't come up with anything

now please let us know about the following

1-what brand test kit are you using @ what resolution?
2- what is the salinity of your mix?
3-are you using any ca reactors ,what is your co2 injection rate? is it on a timer or controller?
4-what is your Kalk dosing schedule & how much & what time how do you mix your Kalk?
5-how often you water changed with the mix you are refering to & what is the xolume?
6-what is your tank size & your total net water volume ?
I am sure other people can chime in as well
However I know Albert is very knowledgable & he can also help you if you paid him a visit ,since he said you are a good guy & a good customer ,I think that be a good Idea as well
Speak to you soon
Regards
Proline

[kwirky]

thanks for helping me troubleshot this.

1-what brand test kit are you using @ what resolution?
aquarium pharmeceuticals calcium kit. reads in increments of 10ppm. reads 440ppm

nutrafin kH kit. reads in increments of 10ppm CaCO3. Reads 120 ppm CaCO3.

salifert magnesium kit. Reads in increments of 30ppm. Reads ~1550 ppm

Milwaukee pH probe calibrated last week. reads in increments of 0.1

Swing needle meter hydrometer. Heard they're just as accurate, but I haven't checked to see if I have to adjust it's readings. Deep Six, reads in increments of 0.001 but you can guestimate to .0005 or so by looking at it.

2- what is the salinity of your mix?
1.025 in my tank

3-are you using any ca reactors ,what is your co2 injection rate? is it on a timer or controller?
nope, dripping kalk

4-what is your Kalk dosing schedule & how much & what time how do you mix your Kalk?
I mix up a fresh batch. at about 5 in the evening. I mix 1 tsp Seachem kalkwasser in a 4L jug of RO/DI water. Then start dripping it at about 11pm before I go to bed (the lights are just about to turn off then).
I set the drip rate to about 1 second per drop through airline tubing. When I wake up in the morning (7 am), each morning it's seized up, and only dripped 1/4 of it. I loosen the airline tubing to continue the drip. Seizes up again at about 7 pm, and I loosen it again.

I mix new kalkwasser about every 2 days, and each mix is dripped over 1.5 days.

5-how often you water changed with the mix you are refering to & what is the xolume?
the system was started with tap water. I used the last of my seachem reefcrystals, mixing 70% oceanpure, and 30% seachem salt.
The subsequent water changes have been with RO/DI water, and oceanpure salt.

The tank is a month old. 3 days in I did a 30% water change. 3 days in again, did another 30%. 1 week later I did a 10% change, and another week i did another 10%.

I've been planning on doing a 10% water change every 2 weeks now that the nitrates have been stable for over 2 weeks.

6-what is your tank size & your total net water volume ?
tank is 120 gallons. Sump is filled to 15 gallons. I'm guestimating the total water volume is about 120 gallons considering displacement of the liverock and sump space.

I added 6 tsp of baking soda mixed in the 4L jug last night at 12:30 pm, dripped at about 2 drops per second to prevent clogging.

Right now (4:10pm), my system's at:
pH 8.2
alkalinity still at 120ppm. Hastn't seemed to budge after adding the calcium carbonate.

Another note:

[littlesilvermax]

Originally Posted by kwirky

aquarium pharmeceuticals calcium kit. nutrafin kH kit.
salifert magnesium kit.

Assuming test kits not old or off (any test kit could be off if the titration got a drop of something else in it) I personally only trust salifert.

Originally Posted by kwirky

Swing needle meter hydrometer. Heard they're just as accurate, but I haven't checked to see if I have to adjust it's readings. Deep Six, reads in increments of 0.001 but you can guestimate to .0005 or so by looking at it.

Can be accurate, but have to calibrate via a refractometer, I have seen some off by .005. Go to LFS or friend and ensure accuracy.

[support@proline]

Hi Shaun
I have to agree with little silver max ,you can get salifert or even better you can use an Elos test kit ,Golds carries both or you can just take a water sample to them & have them test it,however a reliable test kit is very important ,specialy for KH & CA.
Also keep in mind that the tank is only one month old @ the early stages & cycling ,minimal Ph swings are expected ,you have the bacteria trying to break down nutrients & get stablished ,in the process a lot of oxygen is used,....
What are the tank inhabitabts @ this point ?
Also would it be fair to say that your kalk dosing ratio is higher @ night?

[kwirky]

in the tank's a royal gramma, and about 6 softy/LPS frags/very young colonies. I've been feeding 1/2 a pea sized fragment of frozen angelfish mix to the gramma once a day.

I'll take my hydrometer into gold's to get it compared, and I'll take in a sample of water to test.

Yeah, I think it's new tank syndrome causing the pH swings. My skimmer wasn't working properly for a while, too. Had to remove and clean out the air valve.

I think all these problems are just me being inexperienced and I should that I should be patient.

[support@proline]

Don't worry Sean
You 're doing fine ,the important thing is that you are trying to find solutions.
one thing I like to recomend just go slow on stocking the tank ,It always pays up ,I would just be happy with the corals you have & start to stock up in a couple months or so.
As for the PH swingwhat is the min & max ponits?
In what way are your corals responding to the swings ?