pond has been up and running for almost 2 mnths. and have been testing for the ammonia and nitrite rise, just now seeing ammonia reaching 0.50 and nitrite still 0, is 0.50 considered high? genrally how high should it reach before nitrite kicks in? or should i do a partial water change ? will that mess up the bio-cycle? fish are doing fine but dont want to poison them with ammonia , thanks