ph took a nose dive!

Griffer

New member
pH has been stable in my 120 reef since I added a kalkwasser stirrer. Over a 24 hour period is has been steady 8.1 - 8.3. Today, starting at about 8pm the pH dropped from 8.31 to 7.90 at midnight. Usually this tank doesn't hit its low point until mid-morning so something went weird.

The only thing unusual was my wife asked me to start up the propane fireplace (Baby it's cold out there) which hasn't been done since we set up a saltwater tank. This propane fireplace is a ventless design. Is it possible this thing affected the tank somehow?

pH seems to be holding steady at 7.90, hopefully it will go no lower.

Thanks for any insight.

Gene
 

lordofthereef

One reef to rule them all
Gas or wood heat will eat up oxygen in the house. Less oxygen = dropped pH. That certainly can be the cause right there.
 

Randy Holmes-Farley

Reef Chemist
Premium Member
Actually it is not the O2 that caused the drop in pH, but the increase in CO2. More CO2 drops pH. O2 doesn't need to drop much for CO2 to double, since there is a lot more O2 in air than CO2.

Additionally, they do not need to track together in a reef tank at all, with both being high, both low, etc. :)

This graph shows the effect:

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


from it:

Figure 1. The relationship between alkalinity and pH for seawater equilibrated with air containing normal and elevated carbon dioxide levels. The green dot shows natural seawater equilibrated with normal air, and the curves reflect the result that would be obtained if the alkalinity were artificially raised or lowered.

Figure1.jpg
 

coralnut99

New member
I have the same issue when we button the house up for winter and start up the woodstove. It's the kind of thing you need to keep in the back of your mind as the seasons change.
 

Griffer

New member
Well, this is what I was afraid of because starting the propane fireplace was the only thing different from any other day. A ph drop of this magnitude over a 4-hour period can't be good for the critters.

I will have h#ll to pay if I try to tell my wife we can't run the fireplace because I put in a fish tank! Sometimes I think I am on thin ice with it as it is (no pun intended).

Is there a solution not too drastic? I did start the fan that blows across the water surface. Maybe crack a door when the fireplace is on? An air-to-air exchanger? My Apex data graph shows the ph back above 8.0 as of 0730, and climbing.

Any ideas would be good. Maybe me and my tank won't be living in a shed out back after all. :sad2:

Gene
 

Randy Holmes-Farley

Reef Chemist
Premium Member
Lower pH is less desirable, IMO, but the pH swing itself is not much of a concern as long as the extremes of it do not go outside the norms for reef tanks, say, pH 7.8 to 8.5. :)
 

Randy Holmes-Farley

Reef Chemist
Premium Member
No, it is not low O2, as I said, it is excess CO2. To drive out CO2 with tanked O2 will drive O2 way too high. Aeration with normal air is a fine plan, however.
 
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