Flatlined pH!?!?

Velodog2 · Nov 8, 2014

So my pH suddenly stopped changing today. It has for months regularly oscillated diurnally from about 8.1 to 8.4 +/- 0.1 on either end. I dose sodium carbonate automatically 9 times to smooth out the nightly drop. Below is a pic of my apex chart where u can see the usual swing on the left then this morning during the alk adds it flatlined as can be seen on the far right.

I tested my probe and it read 10.0 in the 10.01 test solution. The only thing that changed I can think of was the addition of a second mp10 vortech last night that I got set up and dialed in sometime this morning. I understand about the lack of equilibrium of CO2 driving the pH swings, but it doesn't seem right to me that on a 25 gallon system with one mp10 on full, an overflow, and a skimmer that adding a second circ pump would have that much effect on CO2 concentration.

Besides being really lost I'm also concerned about the potential drop in pH that could occur overnight with it already being so unusually low (8.07 at 9:43 pm - I also did a water change today which dropped it further).

All organisms seem fine btw.

Velodog2 · Nov 9, 2014

Well the overnight behavior was more typical, even though I did not allow the vortechs to go into nighttime slow mode. The pH began to drop right at 9:30 as usual when the last set of main lights shut down. So maybe there is something else happening. I tested the alk at 10.6 last night around 11:00 which is right where I like it to be so I gave an extra shot of sodium carbonate to bump the pH up to 8.2. Will see what happens today. Another possible factor was that I was sick yesterday and spent most of the day lying around in the bedroom where the tank is located, expelling CO2 the whole time I presume. Still it's odd the pH would be so perfectly flat even then.

Randy Holmes-Farley · Nov 9, 2014

I agree let's see what happens going forward. Sometimes it hard to say what is causing something when multiple factors may be at work.

Velodog2 · Nov 9, 2014

I dunno. Today was a bit more normal, although it started out dead flat again until about 2 pm, then it began rising. But it didn't get as high as normal and it seemed to peak pretty much by 5:30which is early. Still, the behavior isn't as strange as yesterday, and it seems to be normalizing somewhat.

Randy Holmes-Farley · Nov 10, 2014

When are you dosing additives during the 24 h day?

Velodog2 · Nov 10, 2014

I dose for alk 9 times where you see the regularly spaced spikes. I intentionally have my pH probe located close to the doser outlet so I can use it to monitor it for malfunction.

The alk is dosed 3 ml at a time at 10:30, 11:00, and 11:30 pm, and again hourly at 6 - 11 am. I try to counteract the nighttime pH drop off without disturbing anyone who may be trying to sleep in the room too much with my cheap and noisy doser. The Ca is dosed 6 times between noon and 6 pm.

Randy Holmes-Farley · Nov 10, 2014

Oh, that makes sense. Then the dosing isn't likely a reason for the flat response.

Velodog2 · Nov 10, 2014

The tank has returned to a more typical behavior meaning no more flatlining, but it still seems volatile. My currently favored theory is about me spending time shut up in that room with the door closed to keep that durned annoying kitten out, and the window closed to keep the cold out, and huffing out the CO2. I suppose the increased circulation could make the tank more "responsive" to changes in the atmosphere as well.