can someone please explain this to me

[dolly_daydream]

my friend as a 50g drum that she fills with water the night before a water change and lets it stand overnight,why would peolple do this,i just use it straight from my tap and put conditioner in it,what advantages does letting it stand overnight have,,she as discus by the way,,

 

[keeper-of-fish]

The purpose of this is to Do the same thing conditioner does and to prepare it for the discus removing the chlorine after siting out over night

 

[Bignose]

If your water company used chlorine alone to treat the water (not chloramine) the chlorine gas can diffuse out of the water in about a day -- thereby making it safe. Also, water can sometimes have a great deal of dissolved CO2 in it straight from the tap, temporarily reducing the pH. I will usually sit my water out for a tank in an old 10g tank before a water change so that the replacing water is the same pH as the water in the tank. Again, a day or so is enough time for the excess CO2 to leave the water. You friend may also be letting the water reach about room temperature.

If your tap water has the same pH and the same hardness and the same temp as the tank water then conditioning is all that is necessary. But, a change in temp, pH, or hardness is a potential stressor for your fish. Sounds to me like she is just being extra cautious (as I usually do).