What are the effect oxygen saturation in fish?

No. For fish it all depends on size of the tank. that is why you see tiny goldfish in tiny tanks. big goldfish in ponds. and fish the size of a bus in the oceans. Plus it will also depend on the...

I think fish get their oxygen from their gills. or water , water has oxygen but im stupid i dont know.

Respiratory acidosis (excess carbon dioxide in the blood)

Using gills, they pass oxygenated water over the gill surfaces, and exchange O2/CO2 much as we do via our lungs.

It filters it out from the water that flow over its gills.you have to know by your self