Enough co2?

[Darkblade48]

Originally Posted by papwalker

@darkblade48
I posted some info regarding CO2 ph effects with buffering.
It is being withheld by the moderator???
I can possibly get it to you on the msg system here if you're keen.
The same chemistry explains why moderate increases co2 can kill fish as most of us animal earthlings use carbonate buffers to transport co2 for disposal.

Links to outside sites are generally reviewed before being allowed, I believe (this is true for new users). I have approved your post.

Thanks for the links; I will be sure to read them in detail. I am a scientist by background, so this is quite interesting to me

[Hoppy]

Originally Posted by papwalker

Most tank plants won't benefit from CO2 because of poor light or more likely poor nutrients in substrate.
I'm sure most here know that plants breath oxygen, they eat CO2.

Even very low light tanks will grow plants better if you use CO2. Tropica research has demonstrated that. And, those of us who have tried it have also noted it.

Also adding CO2 can increase or decrease pH depending on carbonates.

Adding CO2 will always decrease the pH. That actual pH depends on the KH, but the change in pH with added CO2 is always a reduction.

Most importantly, increasing CO2 can kill fish in marginal O2 tanks because of partial pressure issues at the gills. Excel is also a reducing agent so it can also kill fish in marginal O2 tanks.

Excel, used per the Seachem directions, has not been shown to harm the fish in any way. All aquariums need a good dissolved oxygen content in the water. That is the oxygen the fish need to live. With or without CO2 being added, the fish need oxygen. With high levels of CO2, the fish can live with the CO2 much better, and at higher levels, if the water is always near saturation with dissolved oxygen.

[Darkblade48]

Originally Posted by Hoppy

Adding CO2 will always decrease the pH. That actual pH depends on the KH, but the change in pH with added CO2 is always a reduction.

That is what I thought as well.

Originally Posted by papwalker

The carbonic acid concentration decreases so as to bring the system back into equilibrium with the new lower level of CO2.

While the rest of the quoted material is fine, this is the important part. When there is a lower level of CO2 (i.e. CO2 is no longer being injected, or a lower amount is being injected) present in the water column.

With less CO2 being injected, the pH will not decrease as much, resulting in an "increase" in pH (rather, the pH shifts back closer to the initial value before CO2 injection).

[javajive1981]

Originally Posted by Darkblade48

That is what I thought as well.


While the rest of the quoted material is fine, this is the important part. When there is a lower level of CO2 (i.e. CO2 is no longer being injected, or a lower amount is being injected) present in the water column.

With less CO2 being injected, the pH will not decrease as much, resulting in an "increase" in pH (rather, the pH shifts back closer to the initial value before CO2 injection).

Is the effect less if you have a high GH and KH?

[Darkblade48]

Originally Posted by javajive1981

Is the effect less if you have a high GH and KH?

It will be less if you have a high kH, since the bicarbonate will act as a buffer and prevent the pH from dropping too much.

[Hoppy]

Originally Posted by Darkblade48

It will be less if you have a high kH, since the bicarbonate will act as a buffer and prevent the pH from dropping too much.

No, the "buffer" isn't really a buffer. It doesn't resist pH changes. All it does is shift the pH that the water assumes with CO2 in it higher. The change in pH is the same per ppm of CO2 whatever the kH is. i.e. the ppm of CO2 needed to give you a certain pH is directly proportional to the KH of the water.

[javajive1981]

This is why i think i might avoid Co2. I am lucky in that PH is quite stable. I don't want to risk stressing out my fish.