Mystery bucket of chemical - what is it?

[LostboyinVA]

Check with a RV supply store. They should be able to sell you a converter that will allow the use of an old style propane bottle with a new style connector. Decide for yourself if it will be worth the headache though since you won't be able to refill the old style bottles.

[aquarium]

Those are the safe answers on the chemical, and thank you, but I was hoping someone might recognize the container.