Calcium up, pH down--what to do?

[cplawrence]

Since setting up my tank, my parameters have been pretty consistent:
Ca 320 ppm
Alk 9 dKh
pH 8.2

Since my alkalinity was good, I tried adding a bit of calcium chloride to bring up my Ca. I added enough today to raise it by what I estimated would be 20 ppm. That worked as expected, but my pH dropped to 7.8! I am guessing that it would be unwise to continue in this fashion, but what should I do then?

Thanks,
Chris

 

[AMANIQU77]

PWC perhaps? Buffer additives?

 

[cplawrence]

Well, I don't see how a PWC will help seeing as the water I mix will have a calcium level of 320 ppm. As for the buffer, I was under the impression that it would just lead to more problems.

 

[Devilishturtles]

What brand of salt mix do you use?

A PWC would help if your freshly mixed water tested higher. Over time, as the calcium gets used up, it drops. A PWC will raise it back up.

 

[cplawrence]

I understand and I see that I was just not being clear--the water I mix up has always had a Ca reading of about 320 ppm. With the current inhabitants, Ca uptake has been pretty negligible.
The brand is Instant Ocean, btw.

 

[melosu58]

I agree that the PWC will help stabilize your tank. Your calcium needs to be around 400 to 420.

 

[cplawrence]

I agree that the PWC will help stabilize your tank. Your calcium needs to be around 400 to 420.

I am sorry but I don't see how a PWC is going to help when the new SW would have a Ca reading of 320 and that issue has not been addressed....

 

[JG]

Calcium Chloride will break apart in your tank forming calcium ions and chloride ions. The calcium ions have a charge of +2, this means is it short 2 electrons and will react chemically with something that has two extra electrons. Another possibility is that it will combine in a 1:2 ratio with something having a -1 charge.

So your pH drop is most likely the result of the Calcium ions reacting with the carbonate ions in your tank water in the 1:2 ratio. By removing the carbonate ions you will cause a drop in the pH . The addition of a buffer, such as Kent's Superbuffer, into your system would increase the carbonate ions. and bring your pH back up. The buffer also will allow you to increase your Calcium levels

Have fun

JG

 

[cplawrence]

I realize that I do not a great degree of sensitivity in this measurement, but that presumably would have resulted in a decrease in the alkalinity not to mention the fact that what you are describing would lead to the precipitation of calcium carbonate and would not have given a reading in the calcium test.

 

[JG]

Right... but remember that for every one calcium ion, you are taking out two carbonates. You can deplete your carbonate before you run out of calcium. Also calcium carbonate becomes more soluable as the pH decreases.

May not have been the cause of your pH drop... just a thought...

 

[cplawrence]

Right... but remember that for every one calcium ion, you are taking out two carbonates.

Actually, since Ca is a 2+ ion and carbonate is a 2- ion, they would be a one to one ratio.

I hope that my replies aren't being taken as my being unappreciative of the comments given; I am just trying to figure out how I can fix this problem.

Thanks again,
Chris

 

[MarineFlake]

Please test for mg. It should be roughly 3 times the ca level. A good set of numbers to see would be dKH 8 - 11, ca 400ppm with mg at 1200 - 1250 ppm or ca 450ppm with mg at 1350ppm and of course ph 8.1 - 8.3

This is a good general read and may help..

http://www.wetwebmedia.com/alkalinity.htm

Peace.

 

[JG]

"Actually, since Ca is a 2+ ion and carbonate is a 2- ion, they would be a one to one ratio."



Nice catch - I was thinking " bicarbonate ion " which has a 1- charge while thinking of Kents Superbuffer which used sodium bicarbonate as one of the buffering agents.

 

[melosu58]

My calcium stays at 420 with just PWC twice a week. I use oceanic salt. I`ve never tested it before it goes in but I will next time. If you have corals you will experience a depletion of calcium and trace elements. This can easily be restored doing PWC. As i stated earlier Just PWC alone keep mine over 400 which is what you need for a reef tank

 

[cplawrence]

My calcium stays at 420 with just PWC twice a week. I use oceanic salt. I`ve never tested it before it goes in but I will next time. If you have corals you will experience a depletion of calcium and trace elements. This can easily be restored doing PWC. As i stated earlier Just PWC alone keep mine over 400 which is what you need for a reef tank

That may be a solution a bit down the road--switching brands. When I mix Instant Ocean, I am getting a calcium level of 320 ppm (for the freshly mixed SW).

 

[cmor1701d]

IO has been known for a low Ca reading, Oceanic for a high Ca but low pH. Kent has been all over the place but my last two buckets were very low in Alk/pH and Kent found the same in the samples I sent them.
Have you checked your magnesium level yet.

You may need to supplement with something like Kent's superbuffer AND turbo-calc (calcium chloride) till you get a balanced/stable reading.

I have now switched to Tropic Marin which give me better readings on my new mix. I'm still supplementing with Turbo Ca for my corals.

 

[melosu58]

If you have a large coral population it will deplete your calcium. You may need calcium suuplement. I know before I got my RO/DI the guy I got my saltwater from added buffer to the water while mixing it. I have found oceanic to be meeting my needs though

 

[AMANIQU77]

If you may, I consider pwc an effective way of replacing trace elements in your tank. Some of those trace elements are available in fresh water itself and ofcourse your salt. Nitrates are dominantly affected by this pwc.

If you have calcium problems, instead of trying to calculate the chemical ions whatevers (which I highly respect of all of you, by the way, because I now have a clue at what buffers do ion-wise. Thanks! It makes more sense now) why not buy purple up or something and add those additives according to instructions until you get your desired calcium?

They're only about $14 a pop. Saves me a lot of stress trying to get to the bottom of calcium depletion or pwc calcium deficit. Just add more calcium.