Terrible Advice Tuesdays: Match Up Your Top Off Water?
Terrible Advice Tuesdays: The pH of your top off water needs to match the pH of your tank to prevent pH swings.
The rest of the story: There are lots of things to pay attention to on your saltwater tank, and matching up the pH of your top off water to your tank isn’t one of them. Here’s why:
1) I don’t concern myself with hitting the 8.3 pH that so many people say is necessary to have a saltwater tank. I also don’t really care what the pH of a tank is as long as it is between 7.7 and 8.5. Here’s why
2) The amount of water added when your top off pump runs isn’t much and it certainly isn’t much to cause drastic pH swings. In fact, if you are topping off with just RODI water, then you’ll very likely won’t see a pH change at all. The exception here is if you’ve added kalkwasser to your top off water. In this case, the pH of your tank can change a lot and as I’ve said before, as long as the pH rise per top off event isn’t over .03, you’ll be fine.
Also, if you are using kalk in your top off water, then trying to match the pH of kalk-laden water to your tank is a total waste of time as kalkwasser has a very high pH. Trying to bring the pH down could lessen the effects of the kalkwasser.
Forget about matching up the pH of your top off water and spend more time staring at your tank!
Thanks Shannon for passing this one along.
Browse the Store! Questions?
The buffering capacity of RO water is nil. Another words it will assume the pH of whatever it is added to. This comes from the old Henderson-Hasselbalch equation we all learned in high school and forgot. When we test the alkalinity of the water, we are really testing the buffering capacity. The test is usually a colormetric titration. You are adding drops of an acid and a die that changes from blue to yellow at a certain pH, the more drops it takes the higher the alkalinity or buffering capacity. The higher the buffering capacity the more stable your tank water will be. Sorry if I got too technical, I am a science geek.
Mark S…Henderson-Hasselbalch was pretty cool stuff. Avogadro’s number was awesome too.
Mark, thanks for this valuable tip.
Many different sources say that the absolute value of the pH is not nearly as critical as variations in pH. This somewhat corroborates what you’re telling us. With that said, what about pH variations between day and night? Should we attempt to avoid these fluctuations? If so, what’s the best approach to stabilizing these conditions?
You mentioned that you aim to keep your PH at 7.7-8.3 curious as to why it’s okay to go so low. When were all told to float at around 8.2.
There is one instance where pH matching is crucial… If you are on a deep well.
Water fresh out of the RODI unit will have the same unoxygenated state that the source water will have. Matching pH is a simple matter of dropping in an airstone and allow the water to decant the CO2.
I discovered this the hard way topping off 2 1\2 gallons at once before I invested in an ATO. Yes, bad things happened but a little researching revealed the issue. Now I make and aerate RODI water by the barrelful and pump the aerated water to my ATO.
Things may not always be as they appear or as you would expect. Just sayin 🙂
Having relatively low ph does have its pros like the ability to assimilate calcium into salt water better than with higher ph levels. This is happening in your calcium reactor because of the CO2 injected by the solenoid valve, kalkwasser water can have as high as 1230 mg/Lt i.e. ph of 12.3 if it is stirred, this is why we let the mix of calcium hydroxide settle till clear. I have at times used hydrochloric acid in my kalk making a lower ph around 6.5 – 7.0 plus argoniite thats been melted with acid mixed in my kalk mix to grow calcite coraline flowers as I’ve called them. Thinking I’m nuts as you mite but it works creating beautiful coraline flowers ranging from orange to pink & lavender in color.