i have a 55 gallon and i was wondering how often do i change the filter inserts in the filter? i have just a basic hang on the back power filter, and i was also wondering how to change them since the beneficial bacteria has already built up in the filter if i replace with new filters does that affect the environment. another question is when you do water changes do you just add dechlorinator or add other stuff too like ph buffer. should i just dechlorinate and then test the water? i know these sound like dumb question but my pet store knows as much as i do almost everything they goes against what i have been reading on this forum i just want to learn everything over.