Using Ph indicator for CO2

yashaswibs

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May 31, 2009
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I recently had a unfortunate and expensive accident with overdosing CO2 which killed off most of my fishes. I bought a Milwaukee PH probe and connected the solenoid to it. The tank water was 7.7 in ph (reads 6.0 in my drop checker?!!). I set the ph to 7.0 and switched the gas on- the fishes started to hide, become darker and started to just stay in one place. I immediately switched CO2 off and Ph was 6.9. The fishes did recover.
The questions I have are
1. How much should the PH drop or is it based on GH/KH?
2. Is there a safe way to add CO2 without killing the fishes?
3. Is there any way to check if the CO2 is within normal or optimal range- I have a drop checker mounted inside which was rock solid green (optimum range) ?

Anecdotally, after my discus died i lost interest in the tank and decreased the light to 8 hrs with about 100watt of T5HO and did not check on the tank much- no fert no CO2, no excel- the HC started to grow well into a carpet and the plants are doing quite well, no algae either.
So is it even worth the hassle of CO2?
I did calibrate the meter before using it.
Replies appreciated.
 

abcemorse

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Sep 8, 2008
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1) pH is not a good measure of CO2, too many other things influencing pH

2) Start slowly, monitoring fish closely, increase bps by maybe a bubble at a time, a couple days apart, only when you are home to see any possible stress

3) Are you using 4 dKH solution for your drop checker? If not the colors are meaningless, even at best DC's are an approximate guide, observationof plants and fish is the best indidator for CO2.

I would keep light fairly low till you get CO2 good and consistent, then you can look at increasing light (and CO2, ferts, etc)

CO2 will always help plant growth, even in low light. If it's doing well as is, you might consider the ole if it aint broke line of reasoning, depends on how fast you want stuff to grow.....

HTH
 

yashaswibs

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May 31, 2009
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I hope it is the 4dKh solution that was supplied by the Aquamedic check kit.

Thank you for your reply.
I would love to go by "if it aint broke..." idea but some plants like Rotala Macranda are not doing well- but I guess I could let go of it without feeling bad.

Watching for fish distress is a dicey thing and if I get involved even in things like shopping for a few hours I would worry- but it appears that there are no real alternatives.

Will try it again today and let you know.
Thanks again.
 

dutchy

Plant Guru Team
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Jul 6, 2009
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I'm using a Ph probe too. I'm not really interested in the number on the display, I merely use my fish as a guide to set the level. The good thing of the system is that it compensates for changing conditions, like growing plants. It's also easy because every 0,1 less on the display gives me around 10 ppm more.

My Ph probe tells me Ph is 6.5. With KH 8 that makes 80 ppm of CO2. :rolleyes: The 4dkH dropchecker says that I have 40 ppm. See the confusion? So I removed the drop checker and I kept it at 6.5, because my fish are ok. But if it really says 6,5....6,3 or 6,1....I don't care.

If you had the Ph probe out of the water for some minutes at any time, it dries out very fast. As a consequence, it starts to give false readings which you can only correct by calibrating again.

Don't go shopping when you adjust your CO2.
 

yashaswibs

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May 31, 2009
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I have set the Ph to 7.5- watched the fishes and they did OK, I will observe them for a few more days and decrease the ph a little bit more.
Will keep you updated if anything else goes wrong.
Thanks for your replies.
 

Tom Barr

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Jan 23, 2005
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yashaswibs;43322 said:
I have set the Ph to 7.5- watched the fishes and they did OK, I will observe them for a few more days and decrease the ph a little bit more.
Will keep you updated if anything else goes wrong.
Thanks for your replies.

Unless you have fairly high KH,. drop it to 7.0 and then go down by 0.1pH units for a few days each time.

Regards,
Tom Barr