water changes fresh fish

long story short - I was wondering if you guys could help. I have a new tank with fish they were doing fine I then test for ammonia yesterday. The ammonia was high, come to find out it was rocks that we separated and separately test and each had ammonia. I did a water change last night the ph...

Hi All.   Question about water changes I do a 25% water change each week, Is that a normal amount?, My main question though is I replace the water out of the hose, I treat it with dechlorinater but put it in cold is this harmful to the fish? as someone told me recently it could be?   Thanks    Dan