Ph Question For The Oldies On The Board Please!!

[ohiorn67]

HI, THANKS in advance for the info. I went to the LFS today for my weekly water check. Parameters were:
Alk--norm
Ph--8.1 (home just now it was solid 8.2
ammon-0
nitritrite-0
nitrate--0
calcium 360 (usually I run high just did 1/2 dose of reef complete)
I do a 10% water change every sunday. He was telling me that my PH was kind of between 8.0 and 8.1 and I have had it stead at 8.2 at home..I was saying to him.."well maybe it was because I just took that sample after Just turing my lights on this morning." He said.....LIGHTS have nothing to do with PH....to go home and buffer.....
Well I am doubtful in this advice. Seems to me that my ph was at a solid 8.2 again this afternoon and everything looks great. I do want to keep my CA a little higher so did that 1/2 dose...
I have been worried about PH because I have a new Naso tang and trying to get him to eat I have been putting more food in that usual just the last couple of days. He will not eat anything yet EXCEPT he loves the algae sheets that go on the clip, but I am so afraid of overdoing that. Need help with this and want to hear what you all have to say about this PH info.....
My tank is 90 gallon ( naso is 4 inches will increase tank size by fall but looking for one now) and I have 130 lbs of live rock and several corals. Also have about 1-2 inches of live sand bed. I have the naso, bicolor blenny, pair of maroon clowns and a 6 line wrasse. This completes my fish in this tank until my upgrade.

 

[ophiura]

Your pH is fine. Do not mess with buffer if your alkalinity is normal.
And he is right and wrong. "Lights" do not affect pH, but photosynthesis and respiration do. When lights are on, algae - even if it doesn't look like you have any there is microscopic stuff - breaks into photosynthesis. This USES carbon dioxide, and gives off oxygen. Now, this algae is also respiring and producing CO2 but at this point the reaction favors a decrease in CO2 overall.
Normally, CO2 combines with water to form carbonic acid, or H2CO3. That is the primary acid that causes pH to drop. If alkalinity is good, then the fluctuation in pH should be pretty minimal.
So during the day there is relatively less CO2 in the tank due to photosynthesis by algae (in the light) and the pH will generally go up a bit. During the night, there is no photosynthesis, and to the pH may drop a little bit. The amount of variation depends on your alkalinity...and alkalinity also depends on calcium, and magnesium, and animals/processes in the tank impacting use of calcium
Anyway, does not seem like you need to buffer. Your pH is fine if it is stable. Your calcium is on the low side and so you may want to look into your calcium/alkalinity additives or something.
The pH in general may drop in a sample container over time...basically there would be bacteria in the water that could produce CO2 and drop the pH bit by bit, or there could be aeration, or something in the container itself that affected the pH. But the most accurate pH will be read at the moment the sample is taken.

 

[ohiorn67]

Ophuria....well said!! I feel much better. My alkalinity when I first started this tank was always on the higher side which is where they always told me to keep it. It has since in the last 2 months sat at the normal range. My Ph is reading here exactly what it had been reading the last few weeks. The sample that I took to him was in the car in a small plastic container for about 30-40 min. I added a 1/2 dose of reef complete about an hour ago. I like to be very conservative on this because my calcium usually reads a bit high..so I did a 1 capful dose that is all....then will take a reading tomorrow morning again. I don't like to add much at all to my tank unless I know it has been tested for it. Hey, can you help me put the word out that I am in search of a larger tank or if you hear anyone maybe wanting to get rid of one or upgrade? I would like at least a 135 or better complete setup. I am in tennessee and would be willing to drive a little to get one.
Again, thanks for the info....I feel better....was afraid to dose..did not want to treat what did not need to be treated.....

 

[ophiura]

I'll keep an eye out...
I will also throw in that circulation is another factor in the pH equation, as it influences gas exchange. Don't want to leave that out :yes:

 

[ohiorn67]

thanks, I have 2 power heads in each back corner..one goes to the top for gas exchange, the other towards the front and center of tank for flow...then I have a revolving powerhead in top mid center of tank for circulating back of tank behind rock. Then of course my skimmer...remoraC pro and of course my cannister filter bar which we also have breaking surface. I am kind of neurotic about making sure enough oxygen in my tank...since it is a 90 an a little deeper....so far so good

 

[acrylic51]

Originally Posted by ophiura
Your pH is fine. Do not mess with buffer if your alkalinity is normal.
And he is right and wrong. "Lights" do not affect pH, but photosynthesis and respiration do. When lights are on, algae - even if it doesn't look like you have any there is microscopic stuff - breaks into photosynthesis. This USES carbon dioxide, and gives off oxygen. Now, this algae is also respiring and producing CO2 but at this point the reaction favors a decrease in CO2 overall.
Normally, CO2 combines with water to form carbonic acid, or H2CO3. That is the primary acid that causes pH to drop. If alkalinity is good, then the fluctuation in pH should be pretty minimal.
So during the day there is relatively less CO2 in the tank due to photosynthesis by algae (in the light) and the pH will generally go up a bit. During the night, there is no photosynthesis, and to the pH may drop a little bit. The amount of variation depends on your alkalinity...and alkalinity also depends on calcium, and magnesium, and animals/processes in the tank impacting use of calcium
Anyway, does not seem like you need to buffer. Your pH is fine if it is stable. Your calcium is on the low side and so you may want to look into your calcium/alkalinity additives or something.
The pH in general may drop in a sample container over time...basically there would be bacteria in the water that could produce CO2 and drop the pH bit by bit, or there could be aeration, or something in the container itself that affected the pH. But the most accurate pH will be read at the moment the sample is taken.
I have to disagree to a point "light" does effect PH because it effects photosynthesis. If you take a reading of PH when lights are off it will be lower then when they are on an hour and if you check 4 hours you should get a higher reading. Maybe the guy just worded it wrong

 

[ophiura]

:notsure: Disagree with me? We're saying the same thing, though you've been more concise :thinking: I said he was "right and wrong" and then discussed photosynthesis...light impacts photosynthesis of course which is where he is "right"...but "LIGHTS" (initial emphasis) alone do not particularly impact it which I think was the LFS guy's meaning. He is mostly wrong from what I can tell.

 

[acrylic51]

I know not trying to be a ****but just how you have it worded "lights" don't affect it, threw me way off had to go back and reread what you had said... Sorry

 

[ophiura]

You were definitely more concise and clarified it which I didn't do well. No worries, just was wondering why you disagreed with me