high ph and nitrates with low kh
I have 2 55gal tanks (1 tetra tank, 1 SA cichlid tank). Both of them read high nitrates, amm & nitrites zero. I have been doing 25% water changes 2x a week. I have noticed that my pH is kind of high at 7.6 (tap and tank), where my kH is kind of low at 3 degrees (tap & tank). I have been having random die-offs in both tanks & stressed appearance, lack of color. I have been doing some research and have a question I would like some input on.
Question is: I think I need more buffering capacity (mainly), and a more stable pH which is affected by nitrates(?), nitrate poisioning(?). I am looking at seachem neutral regulator 7.0, and am wondering how to initially dose the tanks. All at once or over several days?
I did an experiment dose in a bucket & got pH 7, and kH 9.
Bottom line is I would like the fish to be as colorful, healthy, active as possible, which includes not dying (of course). Any other suggestions.
Thanks for your help,