x2 on the SeaChem Prime. It has a lower cost per treated gallon than any other dechlorinator. One 5ml capful treats 50g.
You do NOT need to regularly add salt to a freshwater aquarium. It is only needed for the treatment of some diseases, like Ich.
Do NOT worry about having the "correct" pH for your water. Fish need a stable pH far more than the need the "correct" one. If you suffer from wild pH swings, you need to add buffer enhancers.
In general, EVERYTHING you add to the tank increases the osmotic stress on the fish, so even "helpful" supplements can weaken your fish. You need to add dechlorinator because otherwise the chlorine and/or chloramine would quickly kill your fish. Beyond that, most tanks need NOTHING for regular maintenance.
SirWired