Don't know if Shrimp are that sensitive to CO2 to be honest,
Have a 90L (22.5G?) tank, with lots of plants.
On Friday 9th I was in a hurry to go to the office I overdosed the tank with liquid CO2 (put in 6-7 ml instead of 2) and took off.
casualties : 16 of my 27 fish died by the time I got home. I did a 50L water change, but another 7 died by next morning.
did another 50L water change Saturday and a 70L water change on Sunday
2 plecs and 2 botia loaches survived. (tough buggers: they survived a cycling tank too ... beginners mistake)
My 13 Cherry shrimp survived being a 14 hours in high CO2 - low O2 environment (test kit read 0 O2). They no longer are bright red though... they have a mottled red pink complexion. Hope they get bright red again soon
on another note I only know I have 13 left out of 15 because I took evreything out to do the last water change. I rarely glimpse more than 3 at any given time, Leading me to think I had provided my fish with a tasty meal