Hi Shecky, welcome to ]V[ FK
Yes, it is better to be safe than sorry. Water can either be treated chemically or it can be aged like what your friend is doing. However, if you age the water it should still be tested before adding it to the tank. Chlorine evaproates faster than the water but a significant amount in the water to start with may result in some remaining 24 hours later.
Chloramines are in some tap waters. It is the result of the addition of ammonia to the water when the water conditions are so horrible that chlorine will not do the job by itself. The end result is monochloramine which is a stronger oxidizer than chlorine in aquious form (Hypochlorous Acid). When this attacks the sludge in the source water, the end result is polychloramines. Both monochloramines and polychloramines are both toxic to fish and are too large to evaporate indoors at room temperatures (the water evaproates first). You can have your water tested by a swimming pool store; just tell them what you want ahead of time because they will test for all kinds of things that you don't want to buy. They will be plenty cheesed if you waste their time, but they will be more than happy to test for just chloramines
