My 10 gl tank has had two fish in it for one week. They are guppies - named Darth Vader and Orange Fin by my kids My question is how often to test for ammonia levels and how often to do water changes. The info on this site says check twice a day and do large water changes if levels are .25 or greater. I have been having levels of .25 to .5. The folks at the pet store say check every few days and do water changes only weekly or so. Is it somehow bad to do daily water changes if ammonia is present? Are the nice workers at the pet store seriously clueless? Thanks.