I recently began using a pressurized CO2 system that keeps my CO2 at 6.8 in
my 75 gal tank. My tap water is around 7.6 Ph and after several days of
aeration it remains at 7.6 Ph.

One day, I can foresee needing to do a large water change... possibly 50%
for whatever reason... I figure my fish would appreciate me avoiding
dangerously large Ph swings that would happen if I just dumped 35 gal of Ph
7.6 into my 6.8 tank.... I have a couple ideas:

1. Time: make the 50% water change last several hours, thereby buffering
the Ph spike.

2. Artificially lower the Ph of the new water with some type of acid
(Muriatic comes to mind)

3. Lower the Ph with an organic tannic acid such as peat.

4. Reduce my CO2 saturation by 50 percent and raise the Ph within the
operational tank before I do the massive water change.

5. There are probably another dozen ways to do this and I'm soliciting your
experience and ideas!

Do you have any other suggestions? What do some of you do to minimize the
Ph shock during large water changes?

Thanks,

DJay

On Wed, 11 Jun 2003 19:36:07 -0700, "Djay"
wrote:

I recently began using a pressurized CO2 system that keeps my CO2 at 6.8 in
my 75 gal tank. My tap water is around 7.6 Ph and after several days of
aeration it remains at 7.6 Ph.

One day, I can foresee needing to do a large water change... possibly 50%
for whatever reason... I figure my fish would appreciate me avoiding
dangerously large Ph swings that would happen if I just dumped 35 gal of Ph
7.6 into my 6.8 tank.... I have a couple ideas:

I've done large water changes without any problems. The pH shift
doesn't cause any problems. And I think the pH shift will be MUCH
less than you think.

Consider:
I'm guessing your KH is around 4 degrees.

70 gallons of water at 19ppm CO2 = pH 6.8.

After a water change, you'd have
35g at 19ppm, and 35g at 3ppm which would average out to 11ppm,
resulting in a pH of about 7.05.

So, you've got a pH shift of only 2.05.

No problems!


Chuck Gadd
http://www.csd.net/~cgadd/aqua

On Wed, 11 Jun 2003 19:36:07 -0700, "Djay"
wrote:

.....

One day, I can foresee needing to do a large water change... possibly 50%
for whatever reason... I figure my fish would appreciate me avoiding
dangerously large Ph swings that would happen if I just dumped 35 gal of Ph
7.6 into my 6.8 tank.... I have a couple ideas:

......

FWIW,

I have not seen this recommended by anyone, so take my suggestion as
just that - my suggestion. I have been doing this for some time with
no apparent side effects.

After dechlorinating and matching the hardness and temperature, I have
been using Club Soda to match the pH. Be forewarned, a little goes a
LONG way. Seems to me that Club Soda is just CO2 in distilled water
or Carbolic acid. It generally takes about a cup in 8 gallons to
bring my modified tap water to the desired pH of 6.8. Go too far,
just airate it until it dissipates - but this could take a while if
you go too far...

Greg

I have read a lot of banter in the past of talk about pH shock. I'm starting to ask myself, 'are most fish really that sensitive?'

OK, we could go to the extreme and put Discus in a Lake Malawi set up and more than likely have a dead fish! Correct me if I'm wrong, but isn't TDS shock far more of a problem and common that some people realise as opposed to pH shock?

When I do an 80 litre water change in my 300 litre south american tank, I use fresh water with a pH of 7.4-7.6 in a tank at 6.6, no problems. I do always ensure that the R/O water is within a few ppm for each change!

Chuck Gadd wrote in message . ..
On Wed, 11 Jun 2003 19:36:07 -0700, "Djay"
wrote:

I recently began using a pressurized CO2 system that keeps my CO2 at 6.8 in
my 75 gal tank. My tap water is around 7.6 Ph and after several days of
aeration it remains at 7.6 Ph.

One day, I can foresee needing to do a large water change... possibly 50%
for whatever reason... I figure my fish would appreciate me avoiding
dangerously large Ph swings that would happen if I just dumped 35 gal of Ph
7.6 into my 6.8 tank.... I have a couple ideas:

I've done large water changes without any problems. The pH shift
doesn't cause any problems. And I think the pH shift will be MUCH
less than you think.

Consider:
I'm guessing your KH is around 4 degrees.

70 gallons of water at 19ppm CO2 = pH 6.8.

After a water change, you'd have
35g at 19ppm, and 35g at 3ppm which would average out to 11ppm,
resulting in a pH of about 7.05.

So, you've got a pH shift of only 0.205.

No problems!


Chuck Gadd
http://www.csd.net/~cgadd/aqua


I agree with Chuck here and having done monster water changes for many
years, they don't have any effect on the fish, Discus, Cardinals etc.

Your CO2 system will lower the pH down fairly quick, maybe an hour or
two or so.

Regards,
Tom Barr

Chuck,

KH is between 4 and 5 so you're right on the button.
Thanks for the reply and solid science.
Glad to see you're back in the "posting" mode!

DJay


"Chuck Gadd" wrote in message
...
On Wed, 11 Jun 2003 19:36:07 -0700, "Djay"
wrote:

I recently began using a pressurized CO2 system that keeps my CO2 at 6.8
in
my 75 gal tank. My tap water is around 7.6 Ph and after several days of
aeration it remains at 7.6 Ph.

One day, I can foresee needing to do a large water change... possibly
50%
for whatever reason... I figure my fish would appreciate me avoiding
dangerously large Ph swings that would happen if I just dumped 35 gal of
Ph
7.6 into my 6.8 tank.... I have a couple ideas:

I've done large water changes without any problems. The pH shift
doesn't cause any problems. And I think the pH shift will be MUCH
less than you think.

Consider:
I'm guessing your KH is around 4 degrees.

70 gallons of water at 19ppm CO2 = pH 6.8.

After a water change, you'd have
35g at 19ppm, and 35g at 3ppm which would average out to 11ppm,
resulting in a pH of about 7.05.

So, you've got a pH shift of only 2.05.

No problems!


Chuck Gadd
http://www.csd.net/~cgadd/aqua

On Thu, 12 Jun 2003 19:31:06 -0700, "Djay"
wrote:

Chuck,

KH is between 4 and 5 so you're right on the button.
Thanks for the reply and solid science.

Glad it made sense. My first-draft of my reply was simply "don't
worry about it, it doesn't cause problems", but then I decided to
figure out exactly why it didn't cause problems.

Glad to see you're back in the "posting" mode!

My recent tank renovation has helped get me back into things.

I think in the next month or two I'm going to attempt version 2.0 of
my paludarium. It's still up and running, and the plants are going
nuts ABOVE the water level, but the growth under the water is lacking.

If I decide do, I'll be trying to find a new home for the foam/epoxy
rock work. I'd suggest a little bigger tank than my 46g bowfront.
In fact, I'd bet that in a tank that is 18" front to back all the way
across, it would look much better.



Chuck Gadd
http://www.csd.net/~cgadd/aqua