You cant trust ANY pet shop owner most dont know a thing of what their doing. As for water changes, sorry to disapoint you but 30-40% every 3 days is actualy litle, when I have baby turts I normaly change 60% every day or every other day If you can do your 30% every other day would be great. Cloramine wont afect your turt (I think)but use a remover anyway. Also dont scrape anything whit your finger, it may become worse. Insted in case of doubt put your turtle in a bugget with General topic for fish