I use stainless steel (or galvanized steel) bowls.

The only time I use concrete bowls is with problem dogs.

Do not let the water get full of algae as this generally means there are cultures of organisms growing in the water also. Regular changing of the water is essential. However, the algae that grows on the side of steel bowls can be left there, as everytime you re-fill your water tubs with that city water, the algae will act as a filtration system to get all of the chemical impurities out of there.

Jack


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