my air pump broke the other day which ran an air stone in my 400l tank,since it broke my fish has been completely different. he used to sit in the corner twice a day for a good hour when the pump was working and now flies around and hasn't sat once since it broke. food for thought.... fish are annoyed by air stones?
I've never liked them personally and have been put off by the noise the air pumps make, even the so-called "whisper" quiet pumps have an annoying hum to them.
Yes, it certainly sounds like your fish didn't like the air stone or pump much either! Sometimes the buzz from an air pump can reverberate into the water which can bother fish, doesn't happen often but it could be likely in your case.
In reality you should never need an air stone assuming you are using it to get oxygen into your tank rather than any decorative or aesthetic reason?
As long as you have enough movement on the surface of the water and the water is being broken enough at the surface that should be sufficient to get enough oxygen into your tank - I use my filters spraybar to agitate the surface and it works great.
My suggestion - do away with the air stone / extra tubing / pump and use your filter output instead, will save you hassle and a few extra watts in electricity!
yea,it was an eheim pump and was quite quiet but the vibration of the water coming out of the stone was noticeable. i won't be getting a new one. leave the fish in peace i've got enough surface movement from my spray bar.