Just how dangerous to fish are small amounts of dissolved gas?

[MultipleTankSyndrome]

I recently found a way to reduce the dissolved gases in my local water at water replacements by putting the dechlorinator and end of Python in the hang on back filter, so it could splash down, aerate, and remove dissolved gases.
It seems this is removing enough dissolved gases to stop fish getting gas bubbles stuck in their slime coat, but there are still a few gas bubbles on decor and the walls. Are these something I need to worry about (ie: just how dangerous to the fish is this small amount) even though the fish are not flashing, gasping, getting gas bubble disease, etc?

 

[Midwater]

Great question.

 

[duanes]

When I lived in WI, the difference in water temp was significant enough during certain times of year, that water from the tap in winter would often be low 40sF, so super saturated with gases. Even when mixed with hot water, the pressurization from inside the pipes wasn't released until new water hit the sumps surface.
Because water was so cold dissolved gases would turn the new water grey in color, and gas bubble embolism was a possibility.
To cope with this trapped gas buildup, I always added new water to my far end of my sumps first, instead of the main tank, and even then aimed flow against a rock or chunk of wood, or onto the air release bubbles from an airstone, and/or often in effluent splash/flow area. Those obstacles and movement from splash, and traveling thru the sump (and its water pump) sped up off gassing.

 

[MultipleTankSyndrome]

That gives me something of an idea. Even though there's a lot of splashing when the new water drops from the outflow of the filter to the drained level of the tank, the Python end submerged in the filter ends up covered in gas bubbles (suggesting to me that there's not much in the way of aeration until the new water splashes with the old water in the tank).
Perhaps putting an airstone or 2 in the filter body would pre-aerate the water and remove some or all of the gas that the splashing of the water going out can't. And running a few airstones near where the new water comes in could help even further.