cvicente
Active Member
Hello Randy, is there a direct or indirect relationship between carbon dosing and low pH ? Does heterotrophic bacteria produce or release any kind of acids during the denitrification process ?
Low pH and carbon dosing
- Thread starter cvicente
- Start date
- Tagged users None
Randy Holmes-Farley
Reef Chemist
Staff member
Super Moderator
Excellence Award
Expert Contributor
Article Contributor
R2R Research
My Tank Thread
Consumption of the organic under aerobic conditions produces CO2 and lowers pH.
2CH3OH + 3O2 → 2CO2 + 4H2O
Consumption of the organic under anaerobic or hypoxic conditions produces CO2 but also consumes H+ (produces alkalinity) so has a smaller effect on pH (raising it a bit).
12 NO3– + 10 CH3OH + 12 H+ → 10 CO2 + 6 N2 + 26 H2O
2CH3OH + 3O2 → 2CO2 + 4H2O
Consumption of the organic under anaerobic or hypoxic conditions produces CO2 but also consumes H+ (produces alkalinity) so has a smaller effect on pH (raising it a bit).
12 NO3– + 10 CH3OH + 12 H+ → 10 CO2 + 6 N2 + 26 H2O
OP
OP
cvicente
Active Member
Thanks Randy for your prompt reply. A couple of months ago I installed a batch denitrator, first with vodka and more recently with Red Sea NoPoX. The unit flushes every 4 hours and the effluent comes out at 0 ppm for NO3. Since installing the unit I have seen a steady decline on pH. I have always used a calcium reactor and a doser for kalkwasser. I used to have readings during the day between 8.10 and 8.4 now I'm having readings between 7.8 to 8.10. My alkalinity has always been high, 11 to 12 dKH. Corals grow very well but I don't know if the decline in pH could get worse if I don't take action. The pH inside the denitrator just before the end of a cycle is 7.5 to 7.6. The pH meter is calibrated every month with Hach refrences.
Randy Holmes-Farley
Reef Chemist
Staff member
Super Moderator
Excellence Award
Expert Contributor
Article Contributor
R2R Research
My Tank Thread
The denitrator will likely have a mix of aerobic and hypoxic denitrification. I'd just keep an eye on the tank pH that it doesn't go too low (say, below 7.8). You might also consider backing off a bit on the organic in the denitrator until it is just enough to do the job.
Randy Holmes-Farley
Reef Chemist
Staff member
Super Moderator
Excellence Award
Expert Contributor
Article Contributor
R2R Research
My Tank Thread
OK, I'd just watch the pH, but i wouldn't expect the tank pH to continue downwards unless other things change, such as CO2 in your home air.
Myka
Valuable Member
Isn't "a trace" ok? The difference between a trace and "0" is negligible anyway (especially with hobby grade test kits). Maybe see if the 2 mL dosage achieves relatively similar results and possibly less pH impact.
What is NO3 at anyway? The tank looks healthy
Randy Holmes-Farley
Reef Chemist
Staff member
Super Moderator
Excellence Award
Expert Contributor
Article Contributor
R2R Research
My Tank Thread
The choice of organic won't appreciably impact the effect on pH at the end of the process.
OP
OP
cvicente
Active Member
Maybe I used the word "trace" incorrectly, I use a LaMotte Smart 2 Colorimeter to measure PO4 and NO3. If a dose 2ml instead of 3ml the NO3 reading goes up from 0 ppm to 5-8 ppm. Last night I measure the NO3 level and it was at 28 ppm, I feed the fish a lot and I don't use any macroalgae, DSB and do not have a lot of live rock in the system. Before the installation of the denitrator my NO3 was overrange for the colorimeter (above 60 ppm)
OP
OP
cvicente
Active Member
Maybe I used the word "trace" incorrectly, I use a LaMotte Smart 2 Colorimeter to measure PO4 and NO3. If a dose 2ml instead of 3ml the NO3 reading goes up from 0 ppm to 5-8 ppm. Last night I measure the NO3 level and it was at 28 ppm, I feed the fish a lot and I don't use any macroalgae, DSB and do not have a lot of live rock in the system. Before the installation of the denitrator my NO3 was overrange for the colorimeter (above 60 ppm)
OP
OP
cvicente
Active Member
Thanks for your help Randy
Randy Holmes-Farley
Reef Chemist
Staff member
Super Moderator
Excellence Award
Expert Contributor
Article Contributor
R2R Research
My Tank Thread
You're welcome.
Happy Reefing.
Happy Reefing.
mkoenig
Community Member
I have daily ph drops from my denitrator. I can not get the ph over 7.8 in my reef. The water coming out of the denitrator for some reason is 6.9. I have a co2 scrubber on order but not sure if that will help. How do you keep the ph up in a tank when the water coming from the denitrator is low?
Randy Holmes-Farley
Reef Chemist
Staff member
Super Moderator
Excellence Award
Expert Contributor
Article Contributor
R2R Research
My Tank Thread
There are a number of ways to deal with low pH issues, and I would not assume the dinitrator is the only cause (high room CO2 is the normal cause).
Methods include more fresh air to the room, outside or scrubbed air to a skimmer, growing amcroalgae and opther photosynthetic organisms, and very high pH alkalinity additives.
If the dinitrator is the only source of excess CO2, then more aeration will raise the pH.
This aeration test will help diagnose that:
pH and the Reef Aquarium - REEFEDITION
by Randy Holmes-Farley For many aquarists, pH is not something that they have much experience with aside from their aquarium. For many, pH is almost a black box measurement: something to be considered, but whose physical meaning makes little sense to them. This article will Read more here...
www.reefedition.com
The Aeration Test
Some of the possible causes of low pH listed above require an effort to diagnose. Problems 3 and 4 are quite common, and here is a way to distinguish them. Remove a cup of tank water and measure its pH. Then aerate it for an hour with an airstone using outside air. Its pH should rise if it is unusually low for the measured alkalinity (Figure 2). Then repeat the same experiment on a new cup of water using inside air. If its pH also rises, then the aquarium’s pH will rise simply with more aeration because it is only the aquarium that contains excess carbon dioxide. If the pH does not rise in the cup (or rises very little) when aerating with indoor air, then that air likely contains excess CO2, and more aeration with that same air will not solve the low pH problem (although aeration with fresher air should). Be careful implementing this test if the outside aeration test results in a large temperature change (more than 5°C or 10°F), because such changes alone impact pH measurements.
mkoenig
Community Member
It's to cold outside to use that air right now. It would change the water temperature almost immediately. I just installed the CO2 scrubber 5 minutes ago. I plan to do a water change in a little while as well. I have raised the water in that water change with a higher ph to hopefully bring the tank up a little bit. Replacing 30G of a 150. I don't know if the denitrator is the only source but I do know the water coming back out of it is at 6.6 ph right now.
