PH drop when fan is on

[Drauka99]

I have a desk fan mounted under the tank pointed straight down at the sump. The fan is switched on by my APEX when the tank temp hits 78.5. The fan is switched off when the tank temp hits 78 again.
I have noticed for a while now that when the fan comes on that my PH will drop steadily while the fan is running. Once the fan shuts off then PH will slowly rise back to the normal range. I have a removable front to the stand and the back is open as well. I have left the stand front off aand this still occurs. Any clue on whats going on?

I would think I would get a PH increase due to more surface agitation. I also thought that perhaps the stale air under the stand was causing this but that doesn't seem to be the case since I get the same drop even when the stand front is off.

 

[Downbeach]

Any chance of electrical interference?

 

[Drauka99]

I could move the ph probe to the display and see if I get the same drop. The fan is about as far from the ph probe and the apex as I can get it under the stand, ~+2'

 

[fab]

Here is a simple experiment to see if this is an electrical interference problem. Keep fan from blowing at the aquarium in each of these tests.

1. Move the fan so it is not blowing toward the aquarium. Manually turn the fan on for a while that is about the length of time it normally stays on automatically.
Then turn it off for about the same time. Do this ON-OFF cycle a few times. Check the PH behavior.


2. Then move the fan to a different house circuit (different circuit breaker) and run the rest through some more cycles. It would be best to do this last test with the fan plugged into an energy bar and with the energy bar on a different house circuit from the circuit that the PH probe is connected to, that is the circuit its parent module gets power from. Note pH behavior.

3. Repeat test 2 but without the fan's energy bar. Just plug the fan into the house outlet that is on a different circuit.

If the problem occurs in test 1, then it suggests there is no real PH change but the probe is being interfered with electrically by the fan.
If the problem does not occur in test 1, I will be surprised. Then you will need others to step in.

If it occurs in test 2 and 3 Then it further suggests an electrical interference problem caused by the fan. Very likely the motor is emitting an electrical noisy signal that the probe is picking up. The noisy signal may be radiated or it may be conducted through wiring.

If it occurs in test 2 and not test 3, it suggests there may be Apex related paths for the electrical interference problem to take from your fan to the pH probe.

If it occurs in all three tests, it suggests the fan is the source of the problem and the test de-implicates Apex from being involved, other than the pH probe suffering electromagnetic interference.

There is no guarantee that these tests will be unambigously conclusive diagnostically, beyond confirming whether or not the fan is the cause of the pH sensing behavior.

 

[Drauka99]

thanks, I will try those tests.

 

[beaslbob]

If the sump has a refugium or even lotsa live rock/algae, It is possible that the air directly above the sump has lower c02 and higher oxygen. The fin kicks in and makes the air directly above the sump higher in co2 lower in oxygen. Hence more co2 for the sump and the PH falls.

Just a thought

worth at most .02

 

[Drauka99]

I would think if it was that then when I had the stand open to the rest of the room then I would see less of a drop. I had not considered electrical interference from the fan before. I plan to test that theory some in the coming weeks and see what I find.

 

[Randy Holmes-Farley Verified Community Expert]

If there is excess CO2 in the air relative to the tank water, more aeration will lower the pH.

 

[Drauka99]

If there is excess CO2 in the air relative to the tank water, more aeration will lower the pH.

That was it. PH was artificially raised due to dosing. I recently altered my dosing and saw a sharp decline in PH and then stabilization. I have since ran an air line to feed the skimmer outside and saw PH rise from 7.80 to 8.10 over the last few days. I still get dips when the fan is on but now they are much more minor.