I am beginning to see why you have five filters...lol.

I suppose you won't find it mentioned. On the web people read what other people write and then they figure with this consensus info that they are now an authority and then they repeat the same information even if it was incorrect. I'm not saying that your search was not good enough, I am saying that some things come from observation and long experience.

You may have had bubblers in your tanks but for the last time I'm telling you that the principle involved is making the water leaving the filter and entering the tank cry more oxygen. The filter's bacteria have used up a lot of the oxygen already and thus the canister filter's spray bar became a standard item.

You don't place the air stone by the intake tube, you place it beneath the filter outflow whether a spray bar or a nozzle. As the bubbles spread across the surface and break, that is when they aerate. The thin shell of water around the floating bubble is the aerated water. The water flow just under the surface churns oxygenated water with the filter's oxygen poor water.

This makes the water contain more oxygen. A couple of things happen then. 1: More oxygen reaches the filter's bacteria so their performance is boosted. 2: The water circulating in the tank is better oxygenated and stimulates the bacteria on the gravel and rocks etc. 3: the water that EXITS the filter is reoxygenated as it enters the tank.

If you introduced oxygen from an oxygen machine like is used in hospitals (like how people introduce CO2) the same effect would occur.

Just having a bubbler won't do all that much but by locating it so that its upwelling water merges with the oxygen poor water coming from the filter then it does a lot.

You keep on saying that you've operated bubblers before and I have repeatedly tried to explain that just adding bubblers isn't what I have been talking about.