Hi

I have been battling now for a few months trying to sort out my water chemistry.

I use pure R/O DI water, remineralised with Kent R/O Right and pH stable. My problem is I can never seem to attain a pH of 6.8-7.0 with a KH of around 3 degrees. Everytime I reach 3 degrees, the pH ends up close to 8.0!

Presently, I can get the water to about 7.5 with a KH of barely 1 degree. I can bring the pH down in my tanks because I use CO2. It doesn't appear to cause the fish any problems having the new water with a higher pH. The TDS is the same, but I would like to increase the KH to about 3 degrees to be on the safe side to prevent any future pH crashes. I read in a mag the other week someone having a pH of 6.5 and a KH of 6 degrees, this just seems impossible! I am also starting to question the accuracy of my A.P.I KH kit. My pH and TDS are done electronically.

My tank is well planted and blows CO2, below is the water chemistry.


Fresh water Community tank

NH3=0

NO2=0

NO3=10-30mg/L

TDS=200ppm (11 degrees)

KH=0-1 degree

pH=6.8-7.0

PO4=0.5mg/L

Temp=78


All advice welcome.


Cheers

Check out this article, if you haven't read it:

http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

Among other things, it talks about what normal levels of CO2 are, and things
that can throw off CO2 readings.

I use pure R/O DI water, remineralised with Kent R/O Right and pH
stable.

Try leaving out the pH Stable. I believe that's just baking soda. That will
give you a sharp bounce in pH, but it doesn't stay.

What size is your tank, and how much light do you have over it? Also, how are
you adding CO2? (DIY, compressed, some other method?)

Often, if the pH is higher than it should be (based on KH), it means the plants
are stripping all the CO2 out of the water, artifically raising the pH. The
solution is to increase the amount of CO2 you're injecting, or lower the
lighting level.


Leigh

http://www.fortunecity.com/lavender/halloween/881/

"Skunky" wrote in message
...

Hi

I have been battling now for a few months trying to sort out my water
chemistry.

I use pure R/O DI water, remineralised with Kent R/O Right and pH
stable. My problem is I can never seem to attain a pH of 6.8-7.0 with a
KH of around 3 degrees. Everytime I reach 3 degrees, the pH ends up
close to 8.0!

Presently, I can get the water to about 7.5 with a KH of barely 1
degree. I can bring the pH down in my tanks because I use CO2. It
doesn't appear to cause the fish any problems having the new water with
a higher pH. The TDS is the same, but I would like to increase the KH
to about 3 degrees to be on the safe side to prevent any future pH
crashes. I read in a mag the other week someone having a pH of 6.5 and
a KH of 6 degrees, this just seems impossible! I am also starting to
question the accuracy of my A.P.I KH kit. My pH and TDS are done
electronically.

My tank is well planted and blows CO2, below is the water chemistry.

Those numbers look about right to me. There is a diect relationship between
KH, Ph & CO2 levels. Kh of 3 will give a PH of about 7.45 assuming normal
atmospheric levels of CO2 (3ppm). In reality with plants in the tank the CO2
level will be lower than 3ppm and so the Ph will be higher.

You therefore need to add CO2 to an appropriate level.....

At Kh 3.37 dGH (60ppm) you need the following levels of Co2 to get the
corresponding Ph

CO2 Ph
320.8
5.5

254.8
5.6

202.4
5.7

160.8
5.8

127.7
5.9

101.5
6.0

80.6
6.1

64.0
6.2

50.8
6.3

40.4
6.4

32.1
6.5

25.5
6.6

20.2
6.7

16.1
6.8

12.8
6.9

10.1
7.0

8.1
7.1

6.4
7.2

5.1
7.3

4.0
7.4

3.2
7.5

2.5
7.6

2.0
7.7

1.6
7.8

1.3
7.9

1.0
8.0

0.8
8.1

0.6
8.2

0.5
8.3

0.4
8.4

0.3
8.5

0.3
8.6

0.2
8.7

0.2
8.8

0.1
8.9

0.1
9.0



HTH

I.

I use a Hagen yeast CO2 kit at the mo, cheap I know but I have had good results with it, my plants grow well. I intend to buy either the Eheim or Dupla system with pH control module when I can afford it!

My lighting is supplied by 2 Arcadia tubes, original trop and fresh water. Lighting is 10 hours a day.

Cheers 4 the replies.


Stuart

Forgot to mention the tank is 260 litres.

I am aware of biogenic decalcification taking place in the water, my tank doesn't seem to suffer this process to often. The pH is generally quite stable. The problem is the water in my R/O vat, just can't seem to get the pH at 6.8-7.0 with a KH of 3 or 4. I have even tried the phosphate free method as recommended by KENT, still couldn't do it. I e mailed them with this problem, they just said not to worry about as it is fine for a pH reading such as this to have such a low KH!


Thanx

What are Arcadia tubes? Are they compact flourescents? Do you know what their
wattage is?

Forgot to mention the tank is 260 litres.

What are the dimensions of the tank?

The problem is the water in my R/O vat, just can't seem
to get the pH at 6.8-7.0 with a KH of 3 or 4.

So this is not in the tank, no plants, no CO2 injection?

If so, then a KH of 3 or 4 should give you a pH of 7.4 or 7.6.

The "normal" CO2 level of water (no CO2 injection) is about 3ppm. So if you
look at Chuck's chart:

http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

You should be able to find what a "normal" pH is for a given KH. Just look for
for your KH, then go acrcoss the row, looking for the box that gives you 2-3
ppm of CO2. That should be your normal, non-injected pH.

A pH of 8 is definitely a bit high for a KH of 3 or 4. If that's really the
reading you get, I'd say there's something wrong with one of your test kits --
or with the way you're conducting the test. :-) However, you can't expect to
get a pH of 6.8 or 7.0 either, without injecting CO2.




Leigh

http://www.fortunecity.com/lavender/halloween/881/

Skunky wrote:

Forgot to mention the tank is 260 litres.

Skunky,

This tank is far too large for a Hagen CO2 system to help very much. The Hagen system
is rated for tanks of up to 20gallons, approximately 75 liters.

This means that you probably can only drop the pH by one or two tenths of a point at
best until you upgrade to pressurized CO2, or multiple DIY bottles in tandem. Some
people use two, three or even four 2-liter bottles in parallel for larger tanks, but
this eats up a lot of sugar, yeast and time.


The problem is the water in my R/O vat, just can't seem
to get the pH at 6.8-7.0 with a KH of 3 or 4.

Go back to Chuck's chart. At a KH of 3, CO2 diffusion from the atmosphere at
approximately 3ppm will give you a pH of about 7.5. With the Hagen system at full
output, you might be able to drop that to 7.2 for a couple of days.

At a KH of 4, atmospheric CO2 at 3ppm gives you a pH of 7.6, and the Hagen system at
full bore might drop it to 7.3.

Keep in mind that if you have plants and low surface agitation, the plants will
consume the CO2, dropping it down to 1 or 2ppm, and raising the pH accordingly.

So what problem are you trying to solve exactly? Do you want a lower pH? Then add more
CO2. At KH3 and CO2 of 23 ppm, your pH will be 6.6. This will require pressurized CO2
of course.

Also a plant tank can be quite happy at a KH of 2. Here's my tank parameters:

72 Gallons
KH2, GH3
Pressurized CO2
pH 6.4
220 W compact flourescent lighting.

I change 20-25 gallons per week (about 30%). 100% RO reconstituted with Kent RO Right
and Baking Soda. And Leighmo was right, Kent pH Stable is pure baking soda. I use
baking soda from the grocery store.

Thanx for the replies people. I have had a good read on Chuck's site, very informative, has answered all of my questions.

One more thing. Does anybody know where I can gain some in depth info for setting up a 'pure' South American tank from. I have lots of ideas, but the more, the better.


Thanx