High Ca and Low Ph

[Patsfann]

Hello,

Started my tank about 3 months ago, and the ph has been low since the start. Its a 75g, with about 90lbs live rock, some carrib sea substrate, skimmer and low turnover rate via the sump about 300gph estimated.

I am using a Pinpoint ph meter that has been calibrated twice, and recently tested with a Salifert Ph test to verify my reading of 7.65 at night and 7.75 during lighting hours.

The Sg is 1.028, temp 78. Amonnia, Nitrite and, Nitrate are all zero. I just tested the Ca (Salifert) and that measures at the highest reading of the kit at 500ppm.

Also I am using Coral Life salt.



I never actually measured a cycle of the tank, the rock was purchased at a lfs and was cured, in his greenhouse. I did speak with the lfs operator and he did not seemed too concerned about the Ph, and advised me to monitor it as is and just watch for trends?

Thanks for your help

just got my Salifert KH/Alk test and here are the readings,
KH 12.2 (in dKH) and Alk 4.34 meq/L. I do have Seachem reef buffer and reef builder but have not started dosing yet.

OK, I did what Chris suggested and airated some tank water, after about 12 hours of airation the tank ph was 7.70 at a temp of 80 degress. The airated tank water ph was 7.69 at at room temp of 62 degrees.

 

[ChrisRD]

OK, it doesn't sound like you're having any trouble with gas exchange between the tank and the ambient air. Any chance you can try the aeration test outdoors for a couple of hours? That would determine whether or not it's your indoor CO2 levels that are the cause...

 

[Patsfann]

O.K. I airated some tankwater outside for about 9 hours, it was somewhat sunny today, the Ph measured 7.86 at 61 degrees compared to the water in the tank, 7.62 at 78 degrees with the lighting on all day.

 

[ChrisRD]

OK, it sounds like your indoor CO2 levels are a bit higher than outside (which is normal) and that's probably contributing a bit.

Have you tested a batch of new saltwater yet? If so, what do you get for a reading on the new water?

 

[Patsfann]

Hi Chris,

Well this is a little embarrasing but it looks as thought the salwater is the culprit. Measured a new batch thats only been airating for about 7 hours and the ph is 7.74 at 78 degrees. Coral life states the ph should be between 8.2 and 8.3.

So considering all of this would it be ok to use Seachems reefbuffer to raise it to 8.3?

Thanks for all of your help on this.

 

[Anonymous]

Yes it would be OK to use the Reefbuffer to raise the pH.

 

[ChrisRD]

Check the Ca/Alk of the new saltwater. My guess is that since Ca/Alk levels of your system water are elevated and you're not dosing anything, the levels in the new saltwater must also be high. If that's the case, dosing the buffer probably won't be a good idea.

I've never used Coralife salt but can't seem to recall people complaining of low pH with it. In fact, the only test I've seen it in was the old Bingman one from '99 and their results showed that it actually had a high initial pH. It's possible that there's something up with the batch you got or maybe they've changed formulation since then.

The only other thing I can think of at this point is your test readings. I know you've checked the probe against a test kit and the chances are slim that you have bad calibration solutions and a bad test kit, but the readings sound suspiciously low. Any chance you can get your LFS or another local reefer to test your pH?

 

[Patsfann]

Alright,

I checked the calibration on my PH meter, it needed a slight adjustment.
Here are the measurements. It looks like the cause of my low ph high Ca problem is the Coralife salt mix. There is no bioload at this time just live rock. Does this mean I should change to another brand of salt mix?

Date Time Measurement Tank Water New make up water
3/24/2006 3:30 PM Sg 1.028 1.029
Temp 78.8 78
Ph (Pinpoint) 7.76 7.92
Ph (Salifert) 8 8
Ca 500 500
KH 11.2 12.2
AlK 4 4.34

 

[Patsfann]

Hmmm the cut and paste from xcel did not go well in my previous message :/

 

[Patsfann]

different approach,

Date Time Meas. Tank Water make up water
3/24/2006 3:30 PM Sg 1.028 1.029
Temp 78.8 78
Ph Pinpoint 7.76 7.92
Ph Salifert 8.0 8.0
Ca 500 500
KH 11.2 12.2
AlK 4.0 4.34

 

[ChrisRD]

Your Ca and Alk levels are actually pretty well balanced (although high) and at normal CO2 levels I'd expect to see higher pH values. That said, I'm not a chemist and maybe there's something else at work here that I'm not familiar with. :wink:

Looking at the test kit results against the probe it seems the kit is not very sensitive (ie. a 0.16 change on the probe didn't even show-up on the kit). It's possible that your probe may just be reporting slightly low (calibration fluids can be off just a tiny bit and you can see that much error).

Personally I think I would try recalibrating with some new solutions. You might also get a friend or your LFS to test a sample to see what they get.

Either way, at this point I don't think there's much to worry about as your numbers are not dangerously low IMO and I'm pretty confident that your actual pH might be a tad bit higher than what that probe is reporting right now.

You could also try a different salt, although IMO you don't have a big problem and I wouldn't dump your current salt to run out and buy a new one. If it were me I'd just wait until I needed salt and then try something else. I have always had good luck with Instant Ocean and Tropic Marin.

Keep us updated on what happens. This has got me curious now...

 

[The_Big_Fish]

Oceanic Here. Love the stuff.
I have yet to have a problem in any form using it.

 

[Patsfann]

Hi Chris,

I tried before to get the lfs to test my ph and he stated that he does not do that, that i should simply look for trends. At that time i bought some calibration solutions and have recalibrated a couple of times.

Right now I believe I have two choices, trying a few zoa's and or easy fish with the ph as is. Or raise the ph with reef buffer but that worries me because it will also raise my already high Ca. One thing I just read, the dosing instructions for the reef buffer say "If an alkalinity of 6meq/L and a ph of 8.2 has not be attained or substantial cloudiness appears and does not clear within 15 minutes your system is not ionically balanced. to restore this balance do a water change ( I have) or adjust the magnesium and calcium levels to approximately 3:1 Mg:Ca (calcium does not exceed 400mg/L).

At this time I do no have a Mg test kit, any advice about this?

Thanks

 

[The_Big_Fish]

I tried before to get the lfs to test my ph and he stated that he does not do that, that i should simply look for trends

DITCH your LFS and find a new one.



Use a buffer to raise the ph before you add any animals.
Keep an eye on your alk.

 

[Patsfann]

Found another lfs, http://www.lovely-pets.com/ and they were concerned about the low Ph high Ca problem and recommended dosing with Kent Marine's Superbuffer-dKH and said that should raise my Ph and KH. I'll let you know how this goes.

 

[ChrisRD]

Did they know your alk is already high? They may be assuming you have low alk because you have high Ca and thus think the pH issue is due to low alk. Normally it's not a good idea to dose buffer when your alk is already high - especially if your Ca is high too. Driving both levels too high can result in a precipitation event. You can try adding the buffer as an experiment, but I recommend you try it on a bucket of tankwater or something - not in the main system - in case you end-up with precipitate.

I still recommend trying to get different calibration solutions or get someone else to test your pH with a different meter before taking any further action. There's a big club and lots of local reefers in your area so that should be an option. I still think you may be be getting a slightly low (false) reading and that your actual pH may be fine. With a window open or with your skimmer air intake pulling from outdoors, you'd probably see pH come up even more, however, I realize both of those are probably not practical options (especially the window thing considering it's March and you're in Boston :wink: ).

FYI, one way to raise pH is to dose kalkwasser to supplement your Ca/Alk levels when the time comes (you don't need this right now - your Ca/Alk levels are already on the high side). It has a pH raising effect. Just be sure to read-up on it because dosing too much too fast can cause too much of a pH swing and seriously problems.

HTH

 

[Patsfann]

Well to complicate things even more, the store tested my water and thier Ph reading agreed with mine around 7.8 but thier KH reading of 4 was much lower than mine 11.2 and, thats why they recommended that product.

I have given the tank one dose and I suspect that in addition to everything else I am measuring the Kh impproperly, I measured it again, and it should of increased from my previous measurement (considering I dosed with the suppliment). It did not, the measurement went down from 11.2 before the suppliment to 10.2 24 hours later. the ph increased by about .25 in that same time period.

So at this point my low Ph is increasing and the Ca is still high at 500, I need to continue monitoring the Kh because I have to believe the stores reading of 4 due to thier experience and my lack of it. For now I'm gonna take a break and let the tank be for a day or two and then remeasure stuff.

 

[ChrisRD]

Actually, I think that simplifies things. :wink:

If you have low alk and your test results (for alk) were just off all along that could explain the mystery.

If the addition of buffer has shown a positive effect on the low pH situation and your LFS's test showed low alk then I'm guessing that's the case (low alk)...

We sorta went in a big circle here, but I think you've got it figured out now! :wink:

 

[Anonymous]

Well, perhaps not.

Hopefully I'm wrong and just adding Carbonate will easily solve the problem. This just sounds like more than coincidence.

An alkalinity of 4 Meq/L = 11.2dKH. Are you sure their reading of 4 was KH and not Meq/L? A quick phone call should be able to confirm either way.

I only bring this up because of your ALK is 4Meq/L and Calcium is above 500 you will cause trouble by adding more Carbonate to your system.

If they were reading 4KH the that's great news because just increasing Alkalinity should solve your PH problem.

 

[ChrisRD]

Good point and I agree. If the LFS reading was in fact meq/L and not dKH that definitely changes things...