Durvish
Aquarium Advice Activist
Fertilizer run off will hit the water table or filter through the sewer system --- some sewer run off (depending on your water authority) may make it to an actual water source i.e. creek or stream. That effects the natural environment -- to much ferts is not good for mother nature. BUT -- your drinking water is coming from a water treatment plant that monitors **** near everything in your water. With that being said -- there is always a but! -- 1 ppm of Ammonia in drinking water does not have a harmful effect to human ingestion! So your water authority may not care about the rise Ammonia. If it were me I would treat with Prime as if you were treating the whole tank not just the pwc, i.e. if it is a 55 gal tank and you are doing a 50% pwc then treat the whole 55 gal and not just 30 gal you are changing. And last but not least I believe you can over treat with Prime -- I don't have any in front of me but you could check the web site -- I am sure I have read that somewhere.