raising ca reactor effluent pH

[wakesetter]

I have noticed that without my ca reactor on (I ran out of CO2 last week) my pH is quite a bit higher. I have started dripping one gallon of Kalkwasser 2-3 times a week to help raise the pH as well as increasing the Ca and KH levels a bit. When the reactor is on ( I refilled this weekend) I am still not happy with the pH of the tank (7.9-8.1 in the morning and rarely over 8.25 in the evening.) The effluent of the reactor is 7.0 because I am using Carib Seas ARM media which claims to break down at a pH of 7. I am planning on adding a second chamber to the reactor in order to further increase the pH of the tank but I had another idea as well.
In order to try and remove any excess CO2 and increase the pH some more I was thinking about having the effluent drip into an "oxegyn reaction chamber." this would consist of some kind of bottle or chamber or something with an air stone and water in it. The idea being that exposing it to all the air would increase the pH. I was thinking about putting it into my Skimmer intake but thought that the subsequent decrease in the ph of the water in the skimmer would decrease the effeciency of the skimmer.
Any ideas on these thoughts? Or I am I just thinking too much.

[Randy Holmes-Farley]

wakesetter:

In order to try and remove any excess CO2 and increase the pH some more I was thinking about having the effluent drip into an "oxegyn reaction chamber."

That should raise the pH, yes. Whether it will be enough for your needs, I can't say. It will provide an opportunity for some of the excess CO2 to be removed.

There is one small thing working against you here with the likely time constraints in such a system:

In order for CO2 to blow off of the weter, it needs to be in the form of CO2 and not H2CO3. The interconversion between these species can take a few minutes.

At equilibrium in seawater there is hundreds of times more CO2 than H2CO3, so you can easily blow off most of the CO2 leaving a little bit of H2CO3. That may be a big enough effect to be very useful to you.

The thing you won't be able to take advantage of in a short aeration is the shift in equilibrium that given more time would help you drive off even more CO2:

2HCO3- -----> H2CO3 + CO3--

If you aerated for a half hour or more, you'd be able to take advantage of this process to get rid of more CO2.

However, aerating for just a minute or so will help get rid of much of the original CO2 in the sample, and will raise the pH.

The idea being that exposing it to all the air would increase the pH. I was thinking about putting it into my Skimmer intake but thought that the subsequent decrease in the ph of the water in the skimmer would decrease the effeciency of the skimmer.

It seems to be "common knowledge" that lower pH means lower skimmer efficiency, but I can't see any reason that it would be the case, nor have I seen any evidence that it is true. So I am skeptical.