When you see pH drop, you think....

[hng]

Originally Posted by jadefox

So what you're saying is that there are not many acid producing components in a closed system besides CO2 that will suddenly pull down the pH? Unless of course your Alk is way low.

Simple answer is yes. What produces CO2 in a typical closed system? Fish, coral, and bacterial metabolism will all produce CO2, but there will be a fairly stable pH balance due to buffers in the salt water and gas exchange facilitated by protein skimmers and surface agitation. In order to get a dramatic change in the pH (which is already pretty dramatic since it's a logarithmic scale) you have to dump a ton of acid (usually in the form of CO2 reacting with water to produce an acid) into the system (beyond what buffers and gas exchange can handle) or a ton of hydroxide ions. The other occasions are when something is dramatically wrong, such as a bunch of dead fish or disturbing an ancient sand bed. I guess my point is that you shouldn't see a dramatic sudden change in pH if your system is mature and nothing dramatic has changed - if you do, then something is very very wrong.

[jadefox]

Originally Posted by hng

Simple answer is yes. What produces CO2 in a typical closed system? Fish, coral, and bacterial metabolism will all produce CO2, but there will be a fairly stable pH balance due to buffers in the salt water and gas exchange facilitated by protein skimmers and surface agitation. In order to get a dramatic change in the pH (which is already pretty dramatic since it's a logarithmic scale) you have to dump a ton of acid (usually in the form of CO2 reacting with water to produce an acid) into the system (beyond what buffers and gas exchange can handle) or a ton of hydroxide ions. The other occasions are when something is dramatically wrong, such as a bunch of dead fish or disturbing an ancient sand bed. I guess my point is that you shouldn't see a dramatic sudden change in pH if your system is mature and nothing dramatic has changed - if you do, then something is very very wrong.

Agreed. Which is why consistently monitoring very subtle changes in pH can be an effective way to have a handle on the overall health of the tank. Right?

[tdwyatt]

Originally Posted by hng

The first thing I'd check is to make sure the pH probe is correctly callibrated.

This would be the smart thing to do, whether you have just clibrated your meter or not. If you make a ton of changes trying to impact something that is an instrument measurement error, you'll end up really skrewing things up... ...and even clean well-calibrated probes can go instantly bad, so ANY sudden change in pH parameters would demand checking the battery, the reactivity of the probe to a borax solution, or the power supply for the pH meter.

To test your probe for accurate measurements, use the borax test with a batch of freshly made borax solution (sodium mataborate). There are tons of threads here for this topic.

Once the probe has been determined to be capable of accurate measurement of pH, then check the salinity of the tank, the Mg value, and the alks and calcium. All these are interrelated, so that if one is skewed, then most likely all will be, that is just the dynamic of seawater.

Low pH is usually an issue with trapped CO2 or an undiscovered dead specimen/snail producing CO2 and organic acids as it decomposes. Check your parameters, then take roll of your specimens.



HTH

[jadefox]

Originally Posted by tdwyatt

This would be the smart thing to do, whether you have just clibrated your meter or not. If you make a ton of changes trying to impact something that is an instrument measurement error, you'll end up really skrewing things up... ...and even clean well-calibrated probes can go instantly bad, so ANY sudden change in pH parameters would demand checking the battery, the reactivity of the probe to a borax solution, or the power supply for the pH meter.

To test your probe for accurate measurements, use the borax test with a batch of freshly made borax solution (sodium mataborate). There are tons of threads here for this topic.

Once the probe has been determined to be capable of accurate measurement of pH, then check the salinity of the tank, the Mg value, and the alks and calcium. All these are interrelated, so that if one is skewed, then most likely all will be, that is just the dynamic of seawater.

Low pH is usually an issue with trapped CO2 or an undiscovered dead specimen/snail producing CO2 and organic acids as it decomposes. Check your parameters, then take roll of your specimens.



HTH

So again, this wold suggest that constantly monitoring pH is a good litmus test (no pun intended) for overall water quality and aquarium health. A sudden drop in pH is usually an equipment malfunction (e.g. probe or possessed reactor), but a slow decreasing trend should prompt the aquarist to check other parameters. Given the ease with which pH can be monitored with a lab grade probe and an aquarium controller (unlike Alk), it strikes me that pH is indeed a good baseline for aquarium health, or, as Fenner says, "a window into water quality." But what of Whiskey saying Alk is king?

[Wiskey]

Originally Posted by jadefox

So someone who is monitoring hourly for pH would be clued in to a consistent shift downward in Alk by a decreasing pH trend, right?

Maybe,.. or that downward drift is because you fed a whole lot, maybe it's because the lights shut off, or maybe that downward drift is from a little vinager getting in your tank from when you cleaned your glass,.. or maybe it's because your window is shut today, or maybe it's because there are 2 people in your livingroom rather than one that day,.. (That actually makes a bigger difference than I ever thought).

There are simply Way too many things that can effect it to make it worth my while to monitor it like this.

Whiskey

[jamessp01]

I think pH is a decent indicator, but you would need a good baseline to make any judgements. pH is going to vary by time of day, and possibly by time of year. Will vary by evap loss if your doseing kalk, fuge lighting periods, ca reactor tuneing etc.....

Alk, although not as handy to measure, should be maintained at about the same level.

I dont think you can look at one parameter and know for a fact all is well.

[Fly Guy]

I quit ever worrying about ph a long time ago.

I got tired of having to buy new probes and realized it just didnt matter. With excellent surface agitation, fresh air in the room(or in the wintertime feeding my skimmer intake with fresh air), and proper alkalinity levels it never changes anyway besides the usual daily swing

PH should never be treated directly. If everything that affects it is in line.....it will be in line as well.

[Kevin1000]

In my tanks a sudden PH drop would tend to indicate that my PH probe needs changing/calibration or perhaps something has died in the tank.

Over the yrs the PH in my tanks have tended to work pretty consistently and I have resolved that when my PH probes finally bite the dust I am not going to replace them. I will focus on monitoring alkalinity and relying on observation and my nose to determine if something has died.

[jadefox]

Originally Posted by Wiskey

Maybe,.. or that downward drift is because you fed a whole lot, maybe it's because the lights shut off, or maybe that downward drift is from a little vinager getting in your tank from when you cleaned your glass,.. or maybe it's because your window is shut today, or maybe it's because there are 2 people in your livingroom rather than one that day,.. (That actually makes a bigger difference than I ever thought).

There are simply Way too many things that can effect it to make it worth my while to monitor it like this.

Whiskey

Whiskey, I'm talking about the aquarist monitoring pH every hour with a probe and controller and not responding to small shifts from hour to hour, but consistent trends over days. I agree that many, many factors will affect the pH from minute to minute, but I'm talking about consistent trends over time. The aquarist who uses a controller and probe to monitor pH should be able to get a very general sense of aquarium health over time and, more importantly, should have a good baseline for knowing when additional testing is justified/necessary to troubleshoot a problem. I agree that Alk (and calcium) are more important measures of the health of the system, but pH trends over time, given it's connection to all the other params and the ease with which it can be tested/recorded w/ probe/monitor/controller, is a very god canary in the coal mine. No?

[jadefox]

Originally Posted by jamessp01

I dont think you can look at one parameter and know for a fact all is well.

Agreed, indeed! This is a hypothetical discussion. :-)

[jadefox]

Originally Posted by Fly Guy

If everything that affects it is in line.....it will be in line as well.

Ya! That's exactly the point. Right? Everything affects pH, so it's a good param to monitor so long as you are only looking at trends over time as an indicator of a need to dig deeper if something is out of whack.

[Fly Guy]

Originally Posted by jadefox

Ya! That's exactly the point. Right? Everything affects pH, so it's a good param to monitor so long as you are only looking at trends over time as an indicator of a need to dig deeper if something is out of whack.

ya...but on alk, surface agitation, fresh air, and clean water............Im not going to allow those things to get out of line in the first place, therefore Im pretty confident that even though I havent tested my ph in nearly two years........I can tell you what is is right now within .15.......probably much closer than that, I say .15 in case someone calls me on it to prove it.......lol

[jadefox]

Originally Posted by Fly Guy

ya...but on alk, surface agitation, fresh air, and clean water............Im not going to allow those things to get out of line in the first place, therefore Im pretty confident that even though I havent tested my ph in nearly two years........I can tell you what is is right now within .15.......probably much closer than that, I say .15 in case someone calls me on it to prove it.......lol

lol....I'm coming up there with a test kit. Then we'll go fishing. Seriously though, of course we're not going to let those get out of whack, but if they did get out of whack, it will show on the pH scale. In other words, knowing the pH isn't the point--knowing if something is out of whack is.

[bosscrab]

So what is one to do if they have their windows open for days at a time?

[Fly Guy]

Originally Posted by bosscrab

So what is one to do if they have their windows open for days at a time?

nothing...that is a good thing. its houses all closed up in the wintertime with little fresh air that result in high co2 levels in the house so no matter how much surface agitation you may have, you dont have the oxygen in the air for good co2/oxygen exchange in the tank

here is good little drill to see how well your tanks surface agitation is as well as how much fresh air you have in the house....

1. measure the tanks ph

2 take a glass of tank water and stir it violently for a minute in the same room as the tank. measure its ph when done

3. take glas oftankwater outside and stir it violently for a minute...then measure the ph

this will identify for you if your low ph could be a water circulation issue or simply a issue of not enough fresh air inside your house