i also changed my filter today because it has been in there for almost a month i have a starter 10gal tank that i got from walmart. Set it up on jan 2nd and has been running since untill the other day i had a fish doing bad and he died yesterday. So i was told to test it while he was dying and have been testing for two days now. I went today and bought 3 more fish an alge eater, upside down cat fish and a femal guppy. While i was at the store i got some new filters because i have never changed it also the gave my some stress coat to put in the tank before i put the new fish in but now i have did a 50% water change and should i put some more in or no??