driftwood & pH

Subject: driftwood & pH

> Could a piece of driftwood in my 135 gallon tank be buffer my pH
> 7.6?  After replacing my gravel 6 months ago after finding out i
> causing my pH and hardness to rise, I haven't been able to get m
> down even after bubbling CO2 into the return line from my filter
> I purchased an RO unit which is probably one of the best investm
> you could do if you live in a state that has as hard of water as
> does (Utah).  I got the hardness down from over 30 ppm to about 
> ppm by diluting the tap with RO water.  The pH of the tap is 7.6
> and when mixed with RO it remains at 7.6.  

30 ppm would be considered very soft to start with.  I assume you 
know the difference between general hardness and "carbonate 
hardness". (AKA buffering capacity) This is what is important when 
you are trying to balance pH and CO2 concentration.  It is usually 
easiest to stabilize your pH with a KH of between 3 and 6. (this 
is not ppm, but dKH, or "degrees of carbonate hardness)  

> My limited understanding of the chemistry involved leads me to t
> possibilities
> 1-  not nearly enough co2 is being dissovled in the tank, so inc
> the amount bubbled in the return line  (an idea I don't like bec
> almost full grown discus who at last if I remember breath oxygen
> not carbon dioxide),

CO2 does not replace O2 in water.  They can both be present in 
more than adequate amounts.  In fact, if you are using enough CO2 
(as well as light and other nutrients) to promote excellent growth 
in your plants, they will be giving off enough oxygen that you 
will have higher O2 levels than you could ever achieve with other 

> or hook up in my tank the ugly co2 diffuser
> that came with my sandpoint co2 tank to try and diffuse more of 
> gas that is being let out. (those of you who have one know 
> what a big green ugly monster it is, not to mention you have to 
> up a powerhead to it)

Without knowing your KH, it's impossible to know your CO2 
concentration, but I'd be very surprised if you couldn't hold your 
chosen pH with supplemental CO2 being fed into an efficient 
reaction chamber.  An efficient recation chamber, however, need 
not be large, ugly or expensive.
> 2- something is buffer my water.  I tested the gravel extensivel
> would raise RO water to about 6.8 and then stop, the only other
> object in the tank is a big piece of driftwood?  I got the impre
> that a decaying piece of driftwood would actually lower pH.

You are correct.  It is highly unlikely that a piece of driftwood 
would raise the pH in your tank.

Karen Randall
Aquatic Gardeners Assoc.
Boston, MA