How low can my ph safely go?

[sherry]

basically I am asking the same question but another way.

Without buffering my kh is about 1.5.
with buffering it is 3 and I use a controller and co2 to bring ph down from a starting point of 6.5 to 6.0.

tom you have suggested not buffering kh anymore. To get the same amount of co2 then, I'd have to let the ph dip into the 5.somethings. I do have SA fish, cacs, tetras, pencils (and a bristlenose pleco.) I have ludwiga inclinata, rotala macrandra, annubias, tonina fluviatalis, umbrosium, wallechi, cabomba, blyxx.

how low can my ph safely go, if the drop is co2 driven?

 

[Tom Barr]

Re: How low can my ph safely go?

Well, with a KH of 1.5, which I had, actually it was 20ppm, so 1.2 or so.....
The pH will be about 6.1 or thereabouts.

If you have other things monkeying with the alkalinity, then perhaps lower.
6.2 should give you 28ppm or so.

Less than the pH issue, the CO2 that gases your fish is much more what should concern you or anyone. Low pH is nothing.
These fish can be found at pH's of 5.0.

Regards,
Tom Barr

 

[VaughnH]

Re: How low can my ph safely go?

On APC Edward is proposing that the lowest pH that CO2 can cause is about 5.0, so pH crashes can only drop the pH that low. He is advocating ignoring KH rather than trying to raise it with bicarbonate of soda. Is this a good idea? I kinda think it is.

 

[sherry]

Re: How low can my ph safely go?

the fish seem fine..

I changed one more thing, I finally added nitrate... I resisted for a while convinced my bioload added plenty. Finally I cut down on feeding to once a day... from twice.. and got a lamotte kit and discovered my nitrates were only 8, so I dosed.. and within four days my stunted macrandra started putting out REAL leaves!!!!

so I will keep the ph at 6, avoid the kh boosters, and see how the plants like it

 

[Tom Barr]

Re: How low can my ph safely go?

On APC Edward is proposing that the lowest pH that CO2 can cause is about 5.0, so pH crashes can only drop the pH that low. He is advocating ignoring KH rather than trying to raise it with bicarbonate of soda. Is this a good idea? I kinda think it is.

Well it depends, if you want some method to measure the CO2, then yes.

Kinda of funny, for all the carrying on he did about PPS and measurements, guessing and all.......he suggest no KH for CO2........the biggest/largest/most important fraction of all the fertilizers in terms of percentage of plant biomass.........

But you need to test for NO3 and PO4 and add "just enough".........okay........
If you want to make a stand about measurements and adding just enough ferts, then it should start with CO2........

"Low KH" is quite another matter.

There are many post going back a decade on low KH (Paul Sears suggested there was nothing at all wrong with a KH of 1 and corrected me here), the fear was that the pH caused issues and that the plants might go after the HCO3......but if you have enough CO2 to begin with, then the plants will leave it alone.

http://fins.actwin.com/aquatic-plants/month.200105/msg00389.html

Low KH references long pre date such musings.
They go back to using CO2 back in the 1970's and 1980's for the hobby when Dupla started selling CO2 systems. I have references going back to 1962 for DIY yeast CO2, but no mention of measuring CO2 in the hobby.

I gave a simple method to measure the CO2 even if you have no KH by raising the KH up to 1, taking a measurement, then doing several RO water changes to remove the rest of the KH while maintaining the same CO2 flow rates.

By maintaining the same CO2 rates, you no longer can use the pH/KH table, but..........now you know the same CO2 rate is being added, so you can assume that the plant's uptake and concentration of CO2ppm is still the same, the KH does not do anything to that, it just affects pH/CO2 measurements is all.

So adding 30ppm at a KH of 1, will still be adding 30ppm at a KH of zero, the rate of CO2 being added has remained the same, you just changed the KH.

Often, most stuff has been hashed over and over in the past. It's wise to look back and see.

The same type of method used to measure CO2 without any KH, can also be used to non carbonate buffered systems such as soft peat tannins water.
You use a sample of tap/something with KH and no to very little peat/tannins to set the CO2, then add the peat back. A large series of water changes can suffice with measurement right afterwards for CO2/KH and then you can back off the water changes and assume the rate of CO2 and the ppm is still the same even though the KH/pH are now being altered.

The same is true for the ADA aqua soil effects on pH/KH.
Do some very large water changes to dial in the CO2.

Regards,
Tom Barr