Instead of one of the stock aquarium dechorinators, you may want to just buy some dry sodium thiosulfate and mix your own.
There some swimming pool type chlorine test kits that are available that measure high chlorine concentrations that would give you an indication of what you need to deal with. (some may be less expensive than the aquarium types)
There some swimming pool type chlorine test kits that are available that measure high chlorine concentrations that would give you an indication of what you need to deal with. (some may be less expensive than the aquarium types)