Hydroton really inert..?

1 water farm filled with 2 gallons of H20 @ ph 5.5, ran the pump for 2 days and when I checked it today the ph was 7. There is no plant or nutes. Just water and hydroton. What would cause that drift? Is the water returning to it's normal level, or hydroton dust causing the spike?

Also, I let the water sit for 3 hours double checking ph before I started the pump and there is foil covering the entire top so no evaporation has occurred.

Btw, H20 started @ 7.5

hmm not to sure, did you clean out your bucket, and air stones, tubing??

oh just thought maybe there was nute residue in /on the root mass that got into your fresh water when you transplanted

It's a brand new water farm, never been used. I had some prob's with a earlier grow. So I was trying to narrow down the ph culprit. As far as I'm concerned hydroton is not inert. When you hook up massive res's the drift is probably very slight, but with only two gallons it's much more noticable. And i'm assuming after many uses hydroton takes on the ph of the solution. If I'm wrong ... Speak up, rather be humble than ignorant

Is this new or used hydrotron?

If it's new did you rinse it with ph 5.5 water?

If it's not did you clean it with H2o2 or another solution to remove excess salts and root matter?

Soak your rocks overnight in water ph'd to 4.0. Repeat and soak again in new water ph'd again to 4.0. Your ph will stabilize right where you want it 5.7-6.0

By the way,your ph spike is definately due to hydroton rocks,but if you soak em @ 4.0,it will become a non issue.