Low pH and Alk

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Murfman

Murfman

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Randy, have what I would call a strange phenomenon question for you; I have a 300 tank with Dart running 2 returns, 2 Tunze Waveboxes and a Gyre 150 for flow. My pH has dropped way down to the point I ordered a replacement pH probe. It was in the 5s and the probe in my CA reactor effluent chamber was reading normal. pH in the chamber goes above 6.8 and solenoid turns on CO2. pH goes below 6.6 and turns CO2 off. I have opened the window at the tank, turned on a fan to add turbidity to the surface, added another power head at the surface and pH has come up to 6.6. New probe is calibrated with new solution and Ca reactor probe calibrated as well. Some corals have bleached but are alive Bubble coral barely open. I have tried adding non baked baking soda and the pH actually goes DOWN, and not up. It does come back to 6.5 or 6.6 in time.

I have turned off the Ca reactor, for now. Added Kalk to my Kalk reactor to try and get it to come up. I even added Kalk powder directly to the overflow (brand new filter socks catch the powder) and I had precipitate for the 1st time all over the tank. Last test showed Ca at 450 and Alk took 1ML and then .2ML to get a color change using a Salifert kit. I also used a Red Sea KH test kit and got dubious results.

Any ideas?
 
Nutramar Foods
Murfman said:
Randy, have what I would call a strange phenomenon question for you; I have a 300 tank with Dart running 2 returns, 2 Tunze Waveboxes and a Gyre 150 for flow. My pH has dropped way down to the point I ordered a replacement pH probe. It was in the 5s and the probe in my CA reactor effluent chamber was reading normal. pH in the chamber goes above 6.8 and solenoid turns on CO2. pH goes below 6.6 and turns CO2 off. I have opened the window at the tank, turned on a fan to add turbidity to the surface, added another power head at the surface and pH has come up to 6.6. New probe is calibrated with new solution and Ca reactor probe calibrated as well. Some corals have bleached but are alive Bubble coral barely open. I have tried adding non baked baking soda and the pH actually goes DOWN, and not up. It does come back to 6.5 or 6.6 in time.

I have turned off the Ca reactor, for now. Added Kalk to my Kalk reactor to try and get it to come up. I even added Kalk powder directly to the overflow (brand new filter socks catch the powder) and I had precipitate for the 1st time all over the tank. Last test showed Ca at 450 and Alk took 1ML and then .2ML to get a color change using a Salifert kit. I also used a Red Sea KH test kit and got dubious results.

Any ideas?
Click to expand...

Unbaked baking soda will lower the pH of seawater, at least when first added.

To be clear, are you suggesting that the pH in your aquarium itself is below 7.0?
 
Randy Holmes-Farley said:
Unbaked baking soda will lower the pH of seawater, at least when first added.

To be clear, are you suggesting that the pH in your aquarium itself is below 7.0?
Click to expand...
That is what the probe is indicating. Like I said, new probe, new solution to calibrate. Calibrated dead on with Milwaukee pH controller.
 
Tidal Gardens
I calibrate by cleaning probe with RO/DI and a tooth brush, rinse in RO/DI and then shake excess water off. Then I put in test solution and let reading stabilize and make adjustment to the screw. I rinse again in RO/DI and shake off excess and test next solution. If I have to, I make adjustment. In this case, I had to adjust to the 7 and the 10 was dead on. Then I rinse and go back to 7 to verify it is not too high or too low from 7.
 
I had been using Lanthanum Chloride to reduce phosphate but it has been over 2 months since I added any.
 
Tidal Gardens
Well, I just don't believe the tank is in the 5's. Maybe the meter is suffering electrical interference.

Try measuring a cup of tank water away from the tank.

Also, not sure if it is possible with your meter, but perhaps if you calibrated backward, with it thinking the pH 7 was really the ph 10, you might get readings below 7 instead of above 7 where they should be.
 
I will test when I get home and will recalibrate the meter. I did test my 29 bio cube with the same probe and it was reading in the 6s as well.

I will take the probe out of my Ca Effluent reactor and place it in the tank, testing once against the other as well. That is controlled by and AC Jr. controller.
 
Top Shelf Aquatics
FWIW, I've seen the pH reports of hundreds, if not thousands of reef tanks, and never once have I seen the pH actually be below 7 except in weird scenarios. I dropped a small chunk of dry ice into my sump as an experiment once and the sump pH dropped into the 5's, but the tank didn't and the system soon blew off the excess CO2.
 
So I re calibrated my probes. When I went to adjust the one on the Milwaukee, the potentiometer would go from 5.8 to over 20 in just a slight adjustment. I think the controller is shot. The AC Jr adjusted and shows tank water at 8.01, last time I checked. That is a much better reading that low 6s and high 5s. Going to work on the ALK reading and adjustment today.
 
Chewy.com
Randy, is it possible to have 0 alk in the tank? I have a new test kit (Salifert) and low reading I come up with 1.2 ml to get color change. pH is 8.1/2 in the AM and 8.3/4 in the PM. Ca is low at 210, Mg is 1280. I need to replace my CO2 regulator since it keep CO2 flowing when the solenoid shuts off.
 
Murfman said:
Randy, is it possible to have 0 alk in the tank? I have a new test kit (Salifert) and low reading I come up with 1.2 ml to get color change. pH is 8.1/2 in the AM and 8.3/4 in the PM. Ca is low at 210, Mg is 1280. I need to replace my CO2 regulator since it keep CO2 flowing when the solenoid shuts off.
Click to expand...

Nope. Remember, more liquid added to get to the color change endpoint means higher alkalinity. I'm not sure what 1.2 mL translates to in that kit, but it doesn't sound like 0 dKH.

0 alk would mean the tiniest drop gets you to the color change.
 
Deltec

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