The amount of Butane in your freezer it quite small,around what's in a 6 pack of Bic lighters. Look at the nameplate, it's usually measured in grams or ounces.
At least it's in copper tubing instead of plastic!
Splashless bleach
I used 1/2 cup Splashless Clorox in my patio fountain to get rid of the Algae!
It foamed over for hours ! But did get rid of the Algae !