what should i do because my tap water has very high nitrates(40) and ammonia (.25) and nitrites(.25) i do a 70% water change every sunday but i can never get my niitrates under 40 and my ammonia sometimes reads .25
I think other have answered this, but how did you test your tap water?
The EPA required maximum level for Nitrate is 10 ppm (10 mg/L), so I would contact the water service you get water from and ask them if they agree. If so, ask them if they will fix this or wait for it to be reported to the EPA.