Impact livestock on pH


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Sep 12, 2018
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Hey All,

I had an interesting experience following the Texas winters storms and it has raised a question for which I can’t find any clear answers.

I have been fighting low-ish pH in my tank for a while, and had worked through a number of steps to try to get my ph up:

I invested in a indoor air quality sensor and uncovered an issue with my hot water heater venting. By fixing this, I was able to get my indoor CO2 levels reduced by a couple hundred ppm and this help my tank a little (raised ph by .05 ).

I started dosing kalkwasser and this helped significantly (raised ph by at least .1).

i do a lot of air exchange in my tank (open top) , but I made sure that the surface was appropriately agitated (using gyres), but didn’t see any real change.

I was a bit limited in my ability to run an external air line to my skimmer, but I did try running a line into a closet behind the tank , but (perhaps obviously) didn’t see any real change.

All of this got me to a steady state ph level that was reasonable, but still too low for optimum coral growth: 7.8 at night and 8.0 peak during the day.

Fast forward to earlier this year when Texas experienced our freeze event. I lost power and water and while I was able to run a portable generator to keep the tank running, the tank heaters couldn’t keep up with the room temps as low as they were.

I thought everything survived even though my water had dropped to low 60s , but a couple of days after I got power back, I lost 3 fish: a small pipefish, a blue leopard wrasse (~5 inches) and an old snowflake eel that I had for almost 10 years (at least 2.5 feet long).

I was sad to lose these fish, but then I noticed something peculiar. My tank ph had increase by 0.1 on average and now stays between 7.9 - 8.1 when it had been 7.8 - 8.0 before. And it has remained this way since (several months now).

As far as I can tell, nothing changed about my tank or environment (house co2 levels were similar to before) other than the loss of this livestock.

Upon reflection, it made sense to me that a large number of livestock that were producing co2 would have an impact on the tank ph, but I haven’t found this mentioned in any articles on reef ph management.

So my question: should we update the conversation on ph to include a discussion of livestock load within the tank?

Interested in your thoughts.

By the way, here is some information on my mixed reef tank: 224g display, ~40g sump, healthy chaeto refugiam, kessil a360 lights with t5, lifereef skimmer, mp40s x 4, 2x gyres, Red Sea pro salt. Other fish: yellow tang, 2x yellow chorus wrasse, 2x very large clownfish, 2x small clownfish, bicolor blend, small damsel, and hawk fish.

Randy Holmes-Farley

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Sep 5, 2014
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Arlington, Massachusetts, United States
Organisms that produce CO2 will contribute to lower pH. That includes nearly all organisms we can see by eye, from fish to corals to worms to copepods, and most bacteria.

Organisms that consume CO2 will raise pH. That includes all photosynthetic organisms during the daylight hours (but they also product CO2 at night). These include most corals, all algae, and some bacteria, and more. This is the reason for the day/night pH swing.