Does the pH seem affected by the strong water flow? (filter on vs. off)
This is a good question. I've got my probe sitting in my "internal sump" so there is a constant pretty strong flow over it. I have found that when I calibrate it each month, it reads about 0.2 off but I don't know if this is due to the flow.
Maybe I should put it in the tank and see if there is a difference...
I installed the probe today. The in-line probe module doesn't purge the air by itself, I had to twist the probe upside down until all the air escaped. This isn't to big of a deal with the way I have my filter setup. I have the filter and solenoid and heater all on one power strip. When I do water changes, I just turn that power strip on, and it pauses everything until I am done with the maintenance. This lets me empty the tank completely without having to prime the canister filter. With quick disconnect valves at both sides, I can keep from air getting into the module. The biggest thing I was worried about, was air entering from turbulence of the fittings. If air getting into the module is really a concern for you, you can purchase the module below for $40, which purges the air automatically.
I will keep everyone updated on how often I have to clean the probe and how having it in-line effects the readings.