I've delt with ammonia before and the best thing to do is go to your local pet store and buy some ammonia reducer that will get rid of it and if your looking to speed up your cycle they have a bottle of stuff for that too, of I get a new tank I put a bunch of it in and I put my fish in within 3 or 4 days. If you are looking for better filtration then it is never a bad thing to go over the tank limit for a tank in fact it better if you have a filter that does at least double the size of your tank, I have a 200 gallon filter on my 72 gal and it works like a charm, never had any problems with it.