"Racf" wrote in message .net...
"gizmo" wrote in message
...
Well what makes me curious is that just a Day after Changing the water
the
PH raises....
I m still looking for factors that might effect the buffering
issue..... I
came over the hardness issue due to the RO system and this is one good
thing.
The only problem is tying to maintain a PH value of 6.8-7.0 (I m
optimistic.....)
I do have 4 tanks which in all I have about the same GH and almost the
same
PH (7.2-7.4)
In my planted one I use a CO2 system and its fully planted with not
many
fish.....
Maybe I 'm missing something about the buffering but are there other
parameters I might look for ?
10x again

Why do use RO in the first place? Plants do NOT need RO nor do they do
better in RO/softer water.

If you pH is rising, the kH is rising.

Well, removing the acid, in this case the CO2 by the plants, will
cause the pH to rise also. After the lights go off, the pH should drop
back down. This cycle will repeat daily. Unless there's enough CO2
being supplied, this is also could be the issue. pH is generally very
stable in a well run planted tank, but adding enough CO2 is the key.

In a lot of my tanks I use only RO water. I add tiny amounts of
Calcium
Sulfate, Calcium Chloride, and Magnesium Sulfate to insure some
electrolytes. I adjust my pH with plain Baking Soda. My pH ranges from
4.0 - 6.0. Maintaining a precise value has never been my desire.

Amen.

RO water has no hardness or buffering. Taking a pH reading is rather
tricky on it. My $75 pH meter tends to read it rather closely to
whatever the pH of the solution I calibrated to. If I calibrate to 4.0,
I tend to get levels just above it. If I calibrate to 7.0, it follows
this closely. Its hard to read since the probe has an influence on it.
The precision of my meter is specified to be .2, which means its not
pinpoint accurate. The accuracy is very limited and is easily
compromised. I understand its short comings and really would not worry
over even a .5 discrepancy. It clearly is most trusted immediately
after a calibration with a solution close to what I intend to measure.
I would probably spend a couple hundred dollars on a better and more
accurate model if I felt that pH was such a vital parameter, but I do
not believe it is. My meter is better than a color change test kit and
that's about it.

Your problem lies in the super soft water for testing the pH. Pure
water pH probes require specialized pH probes, there is no buffer in
the solution(pure waters). Many reading from very soft water readings
have been found to be in error over the years as many have assumed
these common pH probes are able to accurately measure pH in super
soft/pure waters. I have a very nice ion meter and a nice selection of
probes. But for what you do, the TDS meter works well.

After mixing water sources it may take a while before the pH is stable
especially in low buffer environments. RO water will generally take on
the characteristics of the environment its added to, since it has no
buffer. It will dilute the gH and kH, but cannot really affect the pH
directly beyond the dilution affects.

Same came be said about pH for tap water and water changes.

Not sure why you want your pH to be precisely 6.8 - 7.0 all the time?
That would be really tough to do without adding some type of pH
regulating goop into your tank. Fish are certainly not so picky that
such a precise value is required. Some folks are lucky in that their
tap water is at a value deemed perfect so that plain Water changes are
all that is necessary for maintaining a specific value. If my desired
pH was 8.2 - 8.4, I personally would have it made.

Fully planted tank folks often get told that plants prefer a certain
pH range. So they obsess about pH rather than figuring out how to add
enough CO2 gas. It's all about the CO2 and having enough/slight
excess. pH + KH will give the CO2 reading. Removing all the KH as
mentioned will cause problems. 3-5KH/GH is good, don't go less than
about 2-3KH and 3 for GH.

Discus/Angels etc breed fine at a KH/GH of 3-5, so while a breeding
operation might get higher yields with softer water, bare bottom tanks
etc, planted tanks do quite well and look 1000% better. Healthy
plants= healthy fish.
Generally if you are not keeping specialized fish and breeding them
etc, tap water is fine, even if as hard as can be, examples: KH 15/GH
25 etc.
My plants do quite well. They also do the same in soft water KH 3/GH
5.
But the CO2 level is the same in both tanks/nutrients routine etc.
Read up on pH/KH/CO2 on the web.

Regards,
Tom Barr