Why does GFO lower PH?
- Thread starter SPotter
- Start date
RAJOD
Member
Old post but it seems that there was no answer to the question.
So people were thinking the drop in PH was due to corals etc. I have FOWLR tank and do not have any corals.
I put GFO in my sump 2 weeks ago and my PH dropped from 8.3 to 8.0. Its never been 8.0. So I think there may be something to GFO lowering PH that has nothing to do with coral metabolism.
So people were thinking the drop in PH was due to corals etc. I have FOWLR tank and do not have any corals.
I put GFO in my sump 2 weeks ago and my PH dropped from 8.3 to 8.0. Its never been 8.0. So I think there may be something to GFO lowering PH that has nothing to do with coral metabolism.
RAJOD
Member
I don't have a way to test O2 right now. Nothing else was changed in the tank, same skimmer, same flow.
disc1
-RT * ln(k)
Effect on pH? That's absolutely not true. Adding oxygen has absolutely no effect whatsoever on pH. CO2 on the other hand is the primary driver of pH in our saltwater tanks.
disc1
-RT * ln(k)
Nope. This is absolutely wrong. Oxygen has absolutely no effect on pH in any way. It's all about CO2. The oxygen level has absolutely nothing whatsoever to do with it.
disc1
-RT * ln(k)
That's OK, you don't need to know the oxygen level for pH problem. Oxygen has no effect on pH.
You do have a perfect way to get the CO2 level though. CO2, alkalinity, and pH are all locked into a mathematical relationship. If you know any two you can calculate the third.
For your purposes the actual concentration of CO2 isn't all that relevant. You only really need to know that it is elevated or not. You can tell that by how high or low the pH level is.
As Randy noted in post #16 a pH drop could be from residual acid from the manufacturing process in the product you are using. This would be uncommon .
It could also be from a biotic or biotic precipitation of calcium carbonate as I noted in post(#2) and a consequent effect on pH (though drop in pH from a drop in alk would likely correct itself in a short time as CO2 equlibriated with the room air) .
It might be measurement error related to timing of the test or otherwise.
RAJOD
Member
That PH article I read showed that adding an airstone can drive the PH up.
I'm not going to do that. I was just trying to understand how the GFO added more co2 to my tank which in turned lowered the PH.
Adding an airstone can increase gas exchange by creating surface agitation ,thus increasing the amount of surface exposed to the air as a rippled surface is much greater than a still one. If the tank has low pH and room air has normal atmospheric levels of CO2 or less the extra gas exchange would help move CO2 out of the water more quickly. Likewise if the room air is high in CO2 relative to the tank water it could increase CO2 levels in the tank dropping pH.
An airstone also can accelerate oxygen exchange in the same way but that would not effect the pH .
The only way it would affect alkainity as far as I know is via precipitation of calcium carbonate which can occur with or without calcifying organisms . Often it occurs on the gfo itself or on heaters or pumps . This precipitation would reduce the carbonate /bicarbonate ratio ,lowering alkalinty which if it was significant enough could lower pH . If the product in use brought in some residual acid from the manufacturing process it would add H+ lowering pH,though I've never seen a report on that. What gfo are you using?
An airstone also can accelerate oxygen exchange in the same way but that would not effect the pH .
The only way it would affect alkainity as far as I know is via precipitation of calcium carbonate which can occur with or without calcifying organisms . Often it occurs on the gfo itself or on heaters or pumps . This precipitation would reduce the carbonate /bicarbonate ratio ,lowering alkalinty which if it was significant enough could lower pH . If the product in use brought in some residual acid from the manufacturing process it would add H+ lowering pH,though I've never seen a report on that. What gfo are you using?
