You may add chlorine or bromine tablets to the water even on Shabbat. You may also use a pool tester or indicator strips to check chlorine levels as needed. Although indicators that involve changing colors can raise halachic questions on Shabbat, their use is permissible under the current circumstances.

Mikveh surfaces should be cleaned using disinfectant wipes and/or disposable rags with a bleach or alcohol liquid solution.

Yashar Ko’ach and Shabbat Shalom!