OK, What the Heck! Ph problems...

[mapster]

I'm lost.

The ph of my source water after filtration is high, like 9.0. I thought this didn't matter. When I add Seachem marine buffer the ph jumps to around 9.5 - 10.0. Alk reads around 4 dkh before buffer. I have not yet tested the alk after buffer but I imagine its around 6 or so. When I buffer with backing soda the ph initially drops but because the alkalinity sky rockets off the chart the ph shoots back up. When I add IO to the filtered water the ph is 8.3, but because my top off waters ph is so high the tanks ph is at a consatnt 8.7. What is in IO that sets my ph to the correct level? Why are no buffers working.

TIA
MAP

[512148048]

first are you starting with ro/di water then mixing?
if you arnt then that is why your pH is all over the place the things in IO are just the needed trace elements. IO is as close to the sea as the creaters could get to the real ocean but if you want specifics then go try searching for the make up of IO and maby some one with more chem knolege then me can help you to waht is in the IO that is buffering the water i would just say its the Ca and the dkh

[mapster]

its DI water

[tdwyatt]

The pH in the water column for seawater is NOT controlled by the alkalinity, rather it is a function of the amount of CO2 present in the seawater as it is affected by alkalinity in surface waters (like aquaria). Initial dissolution of ASW mixes and buffers will release protons and absorb protons, based on the initial pH of the water column, the total alkalinity of the water column, the concentration of CO2 in the water column, and the atmospheric concentration of CO2 in the atmosphere directly above the water column. The initial changes seen when adding buffers or ASW mixes is due to the activity of the buffers and their initial mixing, dissociation and finding equilibrium based on the presence of the forementioned substances. Dependingon circumstances, it will take well-circulated water anywhere from 1 to 24 hours to find equilibrium with the CO2 present in the water column and the atmnosphere.

"Baking Soda" (NaHCO3) and "Washing Soda" (Na2CO3) have differing ionization constants, and the proportion of these two agents in seawater buffer additives will determine how high the pH will initially rise when added to seawater. The more Na2CO3 in the mix, the higher the mix will initially drive pH as the equilibrium begins to establish itself. Washing soda has a final pH of 12.4 or so when mixed in water alone, baking soda will release small amounts of CO2 into the water column as it reacts with seawater and the concervative elements (and a few local concentration phenomena a well) but will return to 8.2 at 1.025 SG seawater of good conservative proportionality. It is the ability to do this that provides the functionality of buffers in seawater (including borate). Seawater buffering shifts the proportion of bicarbonate and carbonate in a balancing act that allows for the absorption or donation of protons to prevent rapid large shifts in the water column. When you add relatively large amounts of these substance (please add them slowly in high flow areas), the carbonate/bicarbonate system will require whatever time is needed based on the concentration of these substances added. This is dictated by the ionization constants and the pKa of these substances. Le Chatlier's principle then becomes the most significant physical phenomenon that controls the final rate-of-change within a closed seawater system in terms of alkalinity and buffering. Once equilibrium is reached, stability will be established.

With this in mind, never use seawater that has not had time to be circulated for at least six hours if well-agitated and areated, and do not measure the alk in a system until 24 hours after the initial addition of the boosters.

One more thing, if you have chronic problems with either high or low pH, don't make any major changes in your system chemistry until you...

clean yer probe & recalibrate

[mapster]

Thanks TD, I was hoping to hear from you. It will take me a while to digest that info. For the record my ph monitor is new(ish) and recently calibrated. My top off water is stored in a container for a week or so before being introduced into the system. The ph at that point is around 8.8. This container is a brute trash can with a maxi jet 1200 for circulation. The container is covered, should it not be?

Baking soda is what I think started this mess. I must have OD'ed the tank.

Also, not sure if this makes a difference but there is no life in this tank. Zippo. Just a bunch of very dead rock.

Thanks again

[tdwyatt]

Originally posted by mapster
This container is a brute trash can with a maxi jet 1200 for circulation. The container is covered, should it not be?

Baking soda is what I think started this mess. I must have OD'ed the tank.

Also, not sure if this makes a difference but there is no life in this tank. Zippo. Just a bunch of very dead rock.

Depending on what is/was on the rock, the bacterial action of even recruited bacteria (from your skin, the trachcan itself, even from month's old dry rock) will release CO2 as part of the trophic metabolism of decomposition in this rock/storage system. It should have a skimmer, an open top, and some means of replenishing the evaporative losses to maintain salinity. High doses and levels of bicarb in such a system will correct itself over a few weeks' time (the bicarb under these conditions will donate protons and shift to carbonic acid to buffer out high pH, resulting in a degassing of the carbonic acid as the equilibrium adjusts between carbonic acid and atmospheric CO2). It just needs good turbulent circulation at the surface and an exchange potential (i.e., open tops). Put the skimmer on and let it run full bore, it will cook out whatever detritus may form and remove any sinked phosphates and nitrates.

HTH.