Depending on which fish you have, the can probably handle the change. I renewed my DIY CO2 last night and it's still going crazy this morning. In just one hour I had to remove it from the tank because the fish were gasping, still gasping several hours later. All are fine this morning, the big change didn't shock them.
HTH
"Give me th-"
"Oi! Use your manners, be polite, clean your room, do the dishes, have a shower, do your homework and get a job!!!"
" :roll: Whatever"
" :evil: "