Blackwater with just tap water.

Dear all,
I have been growing wild crosses for the past year with daily 50% water changes. They are adults now and I would like to reduce the water changes to once a week.
I would like to do that and try and use organic ways to reduce pH in the tank so the chances of diseases is lowered.
I was thinking of using peat/almond leaves in the canister filter of my BB 75 gallon tank. Should I try doing something else in addition?
Will just adding peat and almond leaves reduce pH with time?