A PH rant

This is my understanding of PH, and I hope this will shed some light on some of the low PH issues that seem to be plaguing many of us- especially during these winter months. PH is rather complicated, but essentially it is a measure of how acidic or alkaline a solution is. Please note that acidic and alkaline are NOT the same as acidity and alkalinity. Acidity and alkalinity are the measure of a solution's (in our case our saltwater) ability to resist a ph shift in one direction or the other. Alkalinity is directly related to how alkaline the solution is. Essentially, assuming there are no acids in the water, the more alkalinity you have, the higher your PH will be. There are many variables that actually lower the PH even though the alkalinity may be high. ANY acid in the water can slightly (or majorly) affect the PH. Some of the various types of acid in our aquarium can include carbonic acid (due to indoor C02 levels, or improper degassing, etc.), nitric acid (high nitrates), and general decomposition. Please note that there are many more types of acid that can lower PH, but these are some major contributors to our systems.

It frustrates me when people advise to simply add buffer to elevate the PH in somebody's aquarium, when there is generally not enough known about the water conditions (or room conditions) to make such advice. I have seen people struggle with a PH of 7.8, but have alkalinity of 14dKh! There are several possible factors that could cause this, and adding more buffer may not effect a solution, but could make matters worse due to possible precipitation, etc. With proper aeration (this is subjective, I know) generally a PH in the "nominal" range can be achieved. However, there are situations that can cause low PH no matter how much aeration you have. For example, high indoor carbon dioxide levels! The carbonic acid is constantly "eating" away at the natual buffers in the water, and effectively keeps the PH depressed. Solutions for this problem are not easy to come by. Some recommend kalkwasser, but this method can come with some risks, and may not completely solve the problem anyways. I have tried kalk, injection of fresh air via TWO skimmer venturies, and still struggle with a PH in the 7.8 range. I have approx 3900GPH turnover in a 155 gallon aquarium, and while some may not believe that this is enough, if I were to add much more I would have a whirlpool!! BUT, when I open a window near the tank for a couple of days.. POOF.. The PH is 8.4 within a week! So, now I just have learned to live with it, and so have my fish (during the cold winter months).

The point of this is not to bash on anybody, but to educate those that may not understand PH very well, and I want them to know that they are not alone. Thanks for listening!!! I can back-up most of this rant with references if needed!!

 

Follow-up

I also realize that you could have a low ph with high alakalinity due to improper aeration, and/or using tightly fitted hoods can cause degassing problems too. But many times I have found the problem to be elevated indoor C02 levels, and aerating with this air will not allow you to get the PH much higher than it already is.

 

pH, technically speaking, is the negative log of the proton (H+) concentration in a fluid. There are three chemical definitions of the word "acid," but the simplest and most useful definition that exists describes an acid as a chemical which releases H+ in water (the others are advanced chemistry fodder). Buffers work by creating a chemical reaction that flows in two directions at once, thereby keeping the proton concentration constant. However, buffers only work in a specific pH range. When used on fluid with a pH that is not within the buffer's range the buffer can actually begin to act as either an acid or a base (depending on specifics).

I will put together an in depth explanation of pH, alkalinity, and other related topics like ORP, DO, general hardness, and calcium hardness as soon as I get a chance. Of course, I will do a search first and make sure no one else has done the same thing yet. Sounds like everyone could benefit from a little clarification.

 

Enjoy
pH by Randy Holmes-Farley

 

Lotzo,

Thanks for the post. After reading several articles (until it gets to the graphs and charts, then my eyes start to glaze over) I'm beginning to understand that fresh air may be the simplest answer to my low pH problem. I have a fairly energy efficient home and while that is great for my utility bills it is not good for my tank.

As I tried yesterday to figure out a simple solution to my problem I kept coming back to the reason for my concern, is there enough available calcium for the few corals and inverts I have? If water conditions (pH at just over 8, dKH 60 ppm) cause calcium to precipitate out, when I do a calcium test am I testing for available calcium? Or is it testing for any calcium (including the powder on the rocks) in the system?

Again thanks for trying to simplify pH.

 

Great article, I agree with you 100%. I am one of those that suffers low ph and have tried EVERYTHING to fix it. The best trick that has worked for me is to leave open a window(1" 1/2) near the tank. In my case, the window is across form the tank and everytime the a/c runs, it sucks fresh air "across" the tank and into my house. Luna

 

Great article--I have found opening up does just what you said.

 

I had a chat with Tangster once and he told me not to bother with PH. He stated it constantly fluctuates and you can never get a good reading. He advised me to just test for DKH as this is directly associated with PH - if your DKH is stable then you PH will be too.
I've followed this advice for 6 months now - and to date i have not had a problem with and of my tanks inhabitants.

 

I used to have a morning ph of 7.8 and a night ph of 8.1-8.2. I tried adding 1/4 teaspoon kalk to my top off water in morning before lights go on and at night after lights are off and my ph is now 8 in the morning and 8.2 at night. My alkalinity reads 7-8 according to API liquid test. I also dose reef builder 2x a week just to keep alkalinity up.

 

So I removed my last post on this thread because I had misspoken. This is what I was trying to say:

Keeping optimal magnesium levels (~1300 mg/L) will help maintain the proper pH because it helps regulate Ca2+ availability, and in turn replaces the calcium cation to form MgCO3. The correct concentration will help release the calcium already present in your system via aragonite sand and LR, thus making it less necessary to dose Kalk or some other calcium supplement. Additionally, MgCO3 acts as a buffer against pH drop because the bond is still weak enough to be broken by a proton.

This explanation is an oversimplification, but at least advances the notion that marine pH is a complex topic and more factors are at play than just how much buffer is present.

Also, be careful when raising low pH back up. If there is ammonia present in your water (hopefully not!), it can turn into ammonium ion when pH drops. The ammonium ion is much less toxic than dissolved ammonia gas and can accumulate unnoticed. When the pH is suddenly brought back up, all the ammonium ion turns to ammonia gas suddenly, and voila--wipeout! Not good.