Use Reptisafe to dechlorinate your water before putting it in the enclosure. It only takes a few drops and works great. I have used it forever and will never go without it as all municipal water systems chlorinate their water.
As for a day night cycle. It does wonders for a snake so long as you have it 1) on an actual cycle with a timer and 2) there are hides sufficient for the snake to retreat to. I switched to one when I got my PVC enclosure and it has actually positively impacted my snake's welfare. If you have the lighting and can get a timer switch then do it. If not then make sure there is ambient light during the day in the room.
Two other things to touch on
As others have said, you must have athermostat for hte heat mat, not an option with ball pythons. They will dig or push down to the bottom of the tank.
Unless you are in a high humid part of the country, aspen is not the best substrate for a glass tank to keep humidity under control. Coconut fiber or cypress mulch are much better alternatives that help with humidity. Coconut fiber is my personal go to substrate.