when i'm doing water transfers, do i have to add chemicals to the water?

when i bought my biorb (yeah i know not very big, but will do for a while), it came with chemicals to remove chlorine i think and another one i cant remember what for.

so i bought some more of the same chemicals form the shop, and when i have done partial water changes, i have used these chamicals in the new water.

however, when i read posts, psople just seem to say they let the water stand in a bucket for a week or whatever, and dont mention anything about adding chemicals..

so.... am i wasting time and money adding the chemicals? do i need them or should i just use plain water that has been left to stand??

thanks

standing water doesnt loose the cloramines. only the clorine. after learning this fact, i quit aging my water, and use a product called biosafe by marineland. it will give false ammonia readings if you use a nessler based reagent in your ammonia tests, but lucky for me, thats not the kind of testing kits i have.