make-up water, buffer

[rick s]

Hi Randy,

I have read all your articles that I could find and understand that you are adamant about not using buffer in a tank.

What about buffering make-up water?

I have a simple system: 90 gallon reef, protein skimmer, UV sterilizer, lightly stocked. No reactors. No limewater. I add calcium and carbonate as needed.

pH stays at 7.9-8.05
Calcium 400-450
Alk 3.3 meq/L

The pH of my DI water is at 6.4. My system evaporates 3/4 of a gallon per day.

Do you recommend buffering make-up water? If so, with what commercial product? If not, may I ask why not? Adding water with that low of a pH seems like a problem to me.

Also, what do you recommend to raise my pH without radically affecting alkalinity?

Thanks in advance!

[jfinch]

What about buffering make-up water?

It's not needed. Although if you are adding buffer to your tank on a regular basis you could add it to your make-up water rather then to your tank, but the end result is the same.

There are definate advantages to using a balanced calcium/alkalinity additive. I would suggest that you look more closely at using one rather then maintaining your levels with calcium chloride and sodium (bi)carbonate.

If it's the pH of the make-up DI water that has you worried then don't sweat it. The pH is likely low because of dissolved CO2 and the water has no buffering capacity. But even if you add buffer to the water to increase the pH that same amount of CO2 will still be in the water. Regardless, adding this unbuffered water to your tank will have ZERO effect on your tank's pH. You're tank is likely to have just as much or more CO2 dissolved in it as your make-up water.

[Randy Holmes-Farley]

I agree. :)

If one is using a buffer to maintain alkalinity (not pH), it can be added to top off water. But the properties of the purified top off water itself do not matter. The pH is not accurately measured with a pH meter or kit, and if the pH reads low, it is never the cause of low pH in a reef aquarium. It has no buffering capacity, so cannot tug the aqaurium pH down. Combining seawater at pH 8.2 with 2% of pure water with a pH of 6.5 will not result in a water with a pH significantly lower than 8.2. The final pH is not just a weighted average of the pH of the liquids mixed.

FWIW, the pH of pure water in contact with air is below pH 7 due to CO2 in the air that enters the water and forms carbonic acid. That is normal.

I use lime in my top off water to supplement calcium and alkalinity. It also raises pH, a nd is the best way to deal with low pH situations.

If you use just buffer, you will slowly raise alkalinity and depress calcium.

What is your aquarium pH?

Here's an article that may help:

Low pH: Causes and Cures
http://reefkeeping.com/issues/2004-09/rhf/index.htm

[rick s]

Regardless, adding this unbuffered water to your tank will have ZERO effect on your tank's pH.

It has no buffering capacity, so cannot tug the aqaurium pH down.

Wow! In all my research I never read that. Thank you so much. You've also convinced me to switch to a balanced additive system. Is B-Ionic still the favored choice?

[Randy Holmes-Farley]

B-ionic is a fine choice in two part additives, IMO.

Less "perfect" but a lot cheaper is my DIY:

A Homemade Two-Part Calcium and Alkalinity Additive System
http://www.advancedaquarist.com/issues/april2004/chem.htm