i have a 55 gallon i bought from petco 2 months ago.what kind of filter and chemicals do i need for a freshwater setup where i can leave the fish in the tank when i do water changes?
Any siphon hose to drain water. Either a short one into a bucket, or a python so you can attach it to the sink.
Prime is one of the best dechlorinators out there.
Drain out 25-50% of the water, match your top up water to the same temp (or close to it), and add the dechlorinator.