Hi again Flyfisherman,
Sorry but i don't agree. Fish need O2 not only h2o(water), try disable any co2 and cover tank with something for long time period and does not matter what's water flow e.g. and then You will see result. Fish can't consumpt o2 from h2o, h2o is water and water is water
not gas.
In daytime period Yours plants use co2 and produce o2, but if plants don't produce then only way to livestock get o2 from air via surface agitation.
O2 going in to tank from Air via surface agitation-movement together with all other gases what present in air, co2 too, that why some plants in low tech can very good grow and live if near at bottom some diffuser simply from air pump, plants get little co2 from air and tank gets o2.
About fish consumtion o2 i agree, result co2, but there is small concentration in bag - more in yours bag air compartment, because when shaking gas come out from h2o, any gas is lightweight and go out from water, that only time question.
And why i told best and simply aclimatisation via same bag for short time - less stress to fish, gain same temp. as in tank water when keep some half hour and adoptation to same water parameters as in tank when You add tank water.
CO2 not only one parameter what is important.
I tried before qurantine tank and think that is waste of time, nervs , resources and stress for fish.
If fish weak or sick i simply don't wanna buy and all.
If You decrease co2 levels in tank for adoptation then i think You can get only stresed other fishes and plants.
Fish adapt to higher levels faster as with lower.
Like for example temperature - fish can adapt fast from 25C to 29C, but if reverse from 29C to 25C then adapt very slowly and very sensitive, the same on salinity and i think other parameters too.
From my expirience if fish healthy You can change temp. and any parameter in 5 sec dramticaly and everything will be fine.
1 year ago due my heater fault i boiled a lot fishes in my low tech kitchen tank, i don't remember exact temperature but been over 45C, believe or not i removed all fishes from boiled water direct to 25C tank, all fins, skins been dramaticaly damaged-boiled, after couple of months fishes been recovered and only 2 fishes died.
Best Regards and Have a Nice Day !