Wow, that would take a lot of blocks! It is a chemical that slowly dissipates into the water over a month's time, depending on the water's chemistry. It is safe for fish, but not plants or crustaceans, molluscs, etc. It is recommended for concrete or rubberized liners, so I guess it would depend on what your fountain is made out of and whether it houses plants, etc, or not.
answered 2 months, 3 weeks ago
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