Alkalinity Problems in a 5000 Gallon Exhibit

[delbeek]

Randy and Craig: I have been running a 5000 gallon reef exhibit since late May. I started with seawater from our well which has a pH of 7.6, alk of 1.5 meq/L and a Ca level of about 380 ppm. I have a lot of live rock and coral in this exhibit. I do water changes every 2-3 weeks depending on when I siphon the tank that amounts to about 5-8% of the total volume. I am using a MKRII calcium reactor with the output at about pH 6.2, alk 5.5-8 meq/L and Ca ??. The output varies since the outflow rate varies over the course of a week and I have to constantly adjust it. I know the reactor is undersized. There is currently no kalkwasser being used.

Today at 2 PM the tank read 528 ppm Ca (Hach kit), 1.25 meq/L alk. (Aquarium Systems kit) and pH 7.8. I have not been able to get the alk over 2.0, I have measured Ca three times .... 480, 430, 528 ... over the last 3 months.

My question is, how did the calcium get so high but not the alkalinity? How can I correct this? Add sodium carbonate?? How can I avoid this in the future?

Aloha!
J. Charles Delbeek

 

[randy holmes-farley]

Charles:

To be honest, I don't understand how the calcium could have risen that much. Using any balanced additive (limewater, the reactor, dissolving sand, or any two-part additives) the alkalinity should have risen by about 9 meq/L for a rise in calcium from 340 to 528 ppm. Maybe it is a faulty test somehow???

If the calcium is really that high and the alkalinity is really that low, sodium carbonate and/or sodium bicarbonate are good ways to correct the alkalinity.

Without knowing how it got that way, it's hard to say how to prevent it in the future.

Good luck!

 

[casey1329]

Hi Randy. Happy holidays!

Any advice you can give me in reaponse to the following would be much appreciated.

I have persistent high alkalinity (4.5), low calcium (250-300) in a 180 reef tank that is heavily stocked with coral -- 45% soft; 45% LPS; 10% SPS).

After using 2 part ESV product for about a year, I discontinued it and started using kalkwasser and calcium reactor to maintain calc/alk levels about a year ago. On rare occasions when I tested, calc and alk were in desired range (2.5/400).

A few weeks ago, I noticed die off of coralline algae and tests (Red Sea calcium and Hack alkalinity) showed Calc at 250 or less and alk at 4.5. I looked for possible problems and noticed flow of CO2 to reactor had slowed to 1 bubble every three seconds so I adjusted bubble flow back to 2 per second. I also thought maybe the kalkwasser is too cold (in fifties) so I added a heater to 30 gallon container to bring temp to 75F. No effect. Neither fixed the problem.

Did some research and following your response to a similar problem, I added turbo-calcium @ 1 tsp per day pre-mixed in RO/DI water, which brought readings back to desired range within a week. But a few days later, readings are back to 4.5/250.

Any idea what is going on and sugestions on how to correct it?

Thanks,

Mike (from FISHNET) Enright

 

[randy holmes-farley]

Hey, Mike, How's it going?

No, I don't have any good explanation of how that could be happening. A likely possibility is a faulty test kit. FWIW, I would have expected it to take more clacium than that to raise it by 150 ppm, unless the tank is quite small.

Here's an article that describes solving calcium problems:

http://www.advancedaquarist.com/issues/nov2002/chem.htm

 

[casey1329]

It must have been the test kit. I got a new Red Sea calcium test kit over the weekend, and I am back within range (400/4.0). BTW, I keep the test kits in an unheated room in my basement where it can drop to as low as 50F. I wonder if this could impact the reliability of the tests. I am moving the kits to another (heated) location.

Great article! I will keep a hard copy in my test kit box. Thanks again.

I see I am listed as a "Junior Member" when my message posts. That's the first time in a long time I've been called junior anything. I like it.

Mike

 

[randy holmes-farley]

I see I am listed as a "Junior Member" when my message posts. That's the first time in a long time I've been called junior anything. I like it.

Hey, I was called a squat squat until I complained about it. Only later did I realize that it was supposed to be a mark of stature.

, I keep the test kits in an unheated room in my basement where it can drop to as low as 50F. I wonder if this could impact the reliability of the tests.

i wouldn't guess so, unless the water being tested was also at the temperature.

 

[delbeek]

Randy, I think I may have found the problem. In running calcium tests on other water sources I became suspicious about the readings i.e. seemed rather high. I contacted Hach and asked about this and it is most likely the the KOH solution the kit uses has lost strength. Since this helps precipitate Mg the high readings I am getting are most likely due to Mg that did not get precipitated. My powder pillows and EDTA are new as of Sept 02 but the KOH solution is the one that came with the kit (probably purhcased some time in 1996 or so). So I have ordered a new one and shall see what my calcium is then!

Aloha!
Charles

 

[randy holmes-farley]

Ah, that would make sense. I hope it is as easy as that.