Who Gives A Fish Forums

Man, pH drops are the worst. My Discus started flashing when it happened. Added some baking soda as a quick fix, but it's not a long-term solution. Coralite's advice on tap mix is solid. Also, how old's your filter media? If it's ancient, it might be time for a refresh.

Is your tank heavily planted? Plants can lower pH at night due to respiration. If so, try adding an airstone to boost oxygen and reduce CO2 buildup. Also, test pH at different times of day to see if it's fluctuating.

Check your water source too. Sometimes RO membranes wear out and let through contaminants that mess with pH. Test your RO water's TDS to make sure it's actually pure.