Too Much Oxygen??

I think you might be doing too much reading 

Diseases like popeye are caused by bacteria not too much oxygen. Having said that I'm sure I read somewhere about fish and bubbles, but I can't remember where.........

The pics on-line of the air diffuser show a black plastic thing which attaches to the filter outflow, a thin see-through tube which attaches to the black thing and a blue plastic thing which attaches to the other end of the thin tube. I'm assuming that this works like the venturi on my Elite Mini filter and my Eheim biopwer, and the blue thing sticks out of the water so it can draw air into the thin tube, which then comes out of the black tube as bubbles. Have I got it right?

The venturis on my Elite Mini and Biopower are adjustable; the plastic thing on the end of the thin tube which sticks out of the water can turn, reducing the amount of air that gets sucked in, and therefore fewer bubbles. Does the blue thing on yours do this? The ends of mine rotate.

I've only ever used the venturis for a day or so. The Biopower is in the tank in the lounge and my husband threatens to make me turn it off if it makes the tiniest sound when he's listening to his music (the bubbles were too noisy  ) and the Elite Mini is in the betta's tank so the flow is turned right down so the venturi didn't work properly.

The idea that you can dissolve too much oxygen into your water seems a bit dim to me.  The amount of dissolved gas is restricted by the temperature and pressure of your water.  This is why, when you first fill your tank, or do a very large water change, as the water heats up, the dissolved gasses are released and you end up with squillions of gas bubbles.

Remember, just because you read something on the internet, doesn't make it true, the same is true of your local fish shop or the Daily Mail.  And that goes for this forum as much as any other site.  I don't believe you can do too much reading, but you don't have to believe it all!